Variants share the parent product's title, description, brand, category, and core images, but each has its own SKU, price, inventory level, and (usually) variant-specific image. The total number of variants is the product of variant-defining attributes — a shirt in 5 sizes × 4 colors generates 20 variants.
Most ecommerce platforms model variants as child records of a parent. Inventory, pricing, and feed syndication all happen per variant. A common modelling mistake is creating separate 'parent products' for each color, which fragments the catalog and damages SEO and the shopping experience.
Operational rule: every variant needs its own GTIN/UPC for retail and marketplace listings. Sharing a single GTIN across all variants of a product is a common feed disapproval reason.