Google product category

The category decides which attributes a listing is expected to carry (a dress has a neckline, a kettle has a capacity), which questions an assistant can match the product to, and which competitors it is grouped with. "Apparel & Accessories" is a category. "Apparel & Accessories > Clothing > Outerwear > Coats & Jackets" is a useful one. Most merchant-supplied categories are the broad one, or the store's own menu name, which maps to nothing.

Merchant Center takes the category in the google_product_category attribute, as the taxonomy's numeric ID (166 is the apparel branch, “Clothing & Accessories” in the UK list) or as the full path. Google assigns every product a category from the data it is given, and the value in your feed takes over only in a few cases (a category with extra requirements, campaigns structured by category, alcohol), so a vague title still earns a vague category, and the attributes that category expects go unasked.

Sighted assigns each product its precise Google product category from the product's own data instead of trusting the store's menu. That category then decides which attributes Sighted writes and how each one maps onto Shopify's taxonomy.