What are product attributes?
Product attributes are the Shopify data that can be used to create a filter option.
A product attribute could be Collection, Price, Tags, Product option (Size, Color, etc.), Vendor, Product type, Percent sale, Stock status, Review rating (from meta field of a third-party app).
Here are the attributes of an example product:
Aside from using a product attribute, you could create a filter option based on Product metafield: How to create a filter option by metafield?
If your Product option has special characters, please reach out to firstname.lastname@example.org in order to find its proper name to use in creating filter option.