Generally this task helps us to decide products from which categories are worth recommending to customers.

In this task you need: 

1. Carefully read both the "Key Product Category" and "Candidate Product Category" to understand categories being compared
2. Check products which appears if you are searching for these categories 
3. Determine the relationship between two product categories
4. Choose an appropriate answer based on determined relationships

In general there are 5 possible results:

1. Key and candidate are accessories of each other. Either key product category is an accessory of candidate product category or vice versa. 
   Rule of thumb: Usage of either product category depends on the other. 
   Examples: Computer and Computer Keyboard
2. Variations or Specializations. They fall under same/similar broad category, but showcases a complementarity of breadth(variations) and depth(specialization). 1) Variations: The two are variations catering for different occasions, preferences, etc. 2) Specialization: One is general and the other is a specialized subset of the general category.
   Rule of Thumb: They serve similar broader shopping purposes but are best suited for different specific occasions or settings, which is beneficial for this customer as a whole. Items do NOT have to be used together at the same time, but contribute together to this customer's shopping goal. So this label indicates that products are complementary to the customer's shopping goal.
   Examples: Garment Steamers -> Travel Garment Steamers, Beverages/Tea → Beverages/Coffee
3. Used together. Products from these categories can be used together or sequentially under the same event/theme/mission/objectives/activities to enhance another's functionality or overall user experience. 
   Rule of Thumb: While not necessarily dependent on each other, neither fall under similar broad category, they collectively contribute to a specific event, theme, mission, or objective, enhancing the overall experience when combined or USED together. 
   Examples: Baby Cream -> Baby Diaper, Shoes/Athletic/Team Sports -> Soccer/Player Equipment/Shin Guards, Personal Cleansing Wipes -> Facial Tissues, Gardening/Trees → Gardening/Seeds/Herbs, Two-piece Swimwear -> Rash Guard Sets 
4. Substitutes. Products or items that can be used in place of each other to fulfill a similar function or need. 
   Rule of Thumb: "Substitutes recommendation" refers to items that fulfill the same or highly similar functions. When these items are purchased together, they result in duplication for the customer. It's important to note that this concept differs from Variation or Specialization for fashion clothing or jewelry recommendations, where a customer may have multiple dresses or bracelets for variety. However, in the case of substitutes, the items are typically interchangeable in terms of their use or purpose. For example, customer will NOT purchase two microwave ovens at the same time, so this is substitutes. On the other hand, customer can purchase two dresses, so this is Variations or Specialization.
   Examples: Grills & Outdoor Cooking/Grills & Smokers/Gas Grills and Grills -> Outdoor Cooking/Grills & Smokers/Charcoal Grills, QLED TV -> LED TV, Headphone → Earbuds
5. Unrelated. Products or items that don't share any functional, thematic, or categorical connection and serve distinct and separate purposes.
   Rule of Thumb: The items don't share a functional, thematic, gender mixed, or categorical connection and don't serve similar purposes. Or there is gender mismatch.
   Examples: Toilet Paper -> Bowl, Women Legging -> Men Legging, QLED TV → Phone

More Examples and Clarifications

Used Together

Can be used together or sequentially under the same event/theme/mission/objectives/activities to enhance another's functionality or overall user experience. They may not be dependent on each other, or fall under similar broad category, but they collectively contribute to a specific event, theme, mission, or objective, enhancing the overall experience when combined.

Variations and Specializations

They fall under same broad category, and showcases a potential complementarity of breadth(variations) and depth(specialization). Items do NOT have to be used together at the same time, but can be purchased at the same time to contribute together to this customer's shopping goal. For example, we could allow "Skirt" to be recommended with "Short" because customer might be looking to complete their wardrobe. 

1) Variations: The two are variations catering for different occasions, preferences, appearances, etc. Note that these products can still be purchased at the same time to increase a customer’s collection’s variation. Such as dresses to increase her wardrobe. 

2) Specialization: One is general and the other is a specialized subset of the general category. 

While not strictly necessary for one another's function, they can enhance the overall user experience, addressing specific needs or preferences to target audience. 

At first glance, items in this group might be mistaken for substitutes because they may belong to the same parent category. Yet, when delved into more deeply, they reveal a nuanced complementary nature, tailored for distinct occasions or environments. These recommendations cater to particular segments like outdoor enthusiasts, frequent travelers, or tech enthusiast. Accurate labeling requires a degree of domain expertise to discern their unique complementary roles.

More examples for Variations or Specialization

Electronics

• Laptops by Use Case: A general-purpose laptop, a gaming laptop, and a graphic designing laptop. They all serve the primary function of being a computer but are optimized for different tasks.

Fashion and Apparel
In fashion and apparel, items are considered somewhat complementary rather than substitutes when they cater to different occasions, despite serving a similar broad purpose. The distinguishing factor is the specific event or setting for which each item is most appropriate.

• Clothing by Season: A summer jacket versus a winter jacket. Both are jackets but designed for different weather conditions.
• Footwear by Function: Regular running shoes and trail running shoes. Both are for running, but one is specifically designed for rough terrains.
• Tops and Shirts: All items are designed to cover the upper body, but their occasion suitability and material composition create distinct niches within the category.
• Bottom Wear: They all provide coverage for the lower body but differ in style, occasion appropriateness, and length.
• Dresses: Dresses inherently serve the purpose of a complete outfit, but their design, length, and occasion specificity can vary widely.
• Activewear: Designed for physical activities, they optimize comfort and functionality. However, each type caters to specific exercises or sports.

Personal Care

• Skincare by Type: A regular moisturizer versus an anti-aging moisturizer. Both provide hydration, but one has ingredients targeting aging signs.
• Haircare Variants: A shampoo for normal hair and another for color-treated hair. Both clean the hair, but one is specifically formulated to protect color.

Electronics

• Laptops by Use Case: A general-purpose laptop, a gaming laptop, and a graphic designing laptop. They all serve the primary function of being a computer but are optimized for different tasks.

Fashion and Apparel
In fashion and apparel, items are considered somewhat complementary rather than substitutes when they cater to different occasions, despite serving a similar broad purpose. The distinguishing factor is the specific event or setting for which each item is most appropriate.

• Clothing by Season: A summer jacket versus a winter jacket. Both are jackets but designed for different weather conditions.
• Footwear by Function: Regular running shoes and trail running shoes. Both are for running, but one is specifically designed for rough terrains.
• Tops and Shirts: All items are designed to cover the upper body, but their occasion suitability and material composition create distinct niches within the category.
• Bottom Wear: They all provide coverage for the lower body but differ in style, occasion appropriateness, and length.
• Dresses: Dresses inherently serve the purpose of a complete outfit, but their design, length, and occasion specificity can vary widely.
• Activewear: Designed for physical activities, they optimize comfort and functionality. However, each type caters to specific exercises or sports.

Personal Care

• Skincare by Type: A regular moisturizer versus an anti-aging moisturizer. Both provide hydration, but one has ingredients targeting aging signs.
• Haircare Variants: A shampoo for normal hair and another for color-treated hair. Both clean the hair, but one is specifically formulated to protect color.

Substitutes

Substitutes are strictly defined to meet all of the following criteria:

• Functionality: Substitutes typically serve the same or very similar functions.
• Target Audience: Substitutes usually target the same audience or market segment.
• Interchangeability: If one product can easily be replaced by another for a specific use without significant loss of performance or change in outcome, they are substitutes.
• Price Point: Substitutes often exist within a similar price range.
• Consumer Behavior in Response to Price Changes: A strong indicator of substitute goods is if the demand for one product increases when the price of its substitute rises, and vice versa.

Difference between Substitutes and Variations or Specialization

• Variations or Specialization: A product that is a specialized subset of a general category, or variation of another product is NOT necessarily a substitute, they maybe potential complements.
• Shared Category Doesn't Mean Substitution: Products in the same broad category aren't automatically substitutes. A mountain bike and a road bike are both bicycles but serve different primary purposes. Running shoes and hiking boots are both footwear but serve different primary functions. They should fall in Variations or Specialization.
• Different Use Cases Means They Are Used Together: Products that could be used together or enhance the experience of each other, even if in the same category, are used together rather than substitutes. For instance, shampoo and conditioner are both hair care products but serve different functions.
• Check for Direct Replacement: A good rule of thumb is to ask: "If one product was unavailable, would the other product directly replace it without ANY alteration in its primary function?" If yes, they're substitutes.

Difference between Variations or Specialization and Used Together 

• Share Similar Broader Category: If items are specialized forms or versions designed for particular situations or preferences within a broader category, they are "Variations or Specialization" .

• Distinct in their Primary Function: If items are distinct in their primary function, but when collectively used in specific scenarios or themes, amplifying the overall experience, they fall in "Used Together In Activities".