BigCommerce describes the concept of product option as "a product option is used for products that come in different variations. Size and color are common examples of product options, but they can also be things like checkboxes or fields for custom text."
Product options have values, for example a "size" product option could have small, medium, large, etc. as values, and a "color" product option could have white, blue, black, etc. as values.
Combinations of product option values make up a variant, for example a medium, blue T-shirt could be one variant of a T-shirt.
BigCommerce classifies product option sets into two types — "optional" and "required."
Optional vs Required Option Sets
Required option sets make a variant unique physical product. "Size" and "color" are good examples of required option sets for a T-shirt, because a small, blue T-shirt and a large, white T-shirt are distinct physical products and must have separate SKUs in your inventory.
Optional option sets don't make a variant a unique physical product. They are often used for customization, such as made-to-order writing or designs on a product. A custom writing/engraving is a good example of an optional option set for a product.
How SKULabs imports product option sets
SKULabs allows you to import optional option set information as order line-item customization metadata.