Variants imply products that come in multiple alternatives. This may be in the form of color or size. Option values could form different combinations, and each could be a new variant for a product. So, one could figure a shirt in different sizes and colors. They would all be variants of the same shirt.
Shopify variants are easy to list over a product page. One can alternately manage the inventory for each variant from over the inventory page. Similarly, when one intends to save specialized information for the Shopify variants, then for each of the variant detail pages, one can add custom fields. This is accomplished by using metafields.