Product Types

Simple Products
Simple products are exactly that. They come as-is with no attribute options for a customer to choose from (size, color, etc.)
Digital Products
Digital products represent items that are not physical and do not ship to a customer. Examples would be audio, video, or text files, and redeemable items such as tickets. Merchants have the ability to set a maximum number of times the customer may download their purchased item and if/when the download link will expire.
Configurable Products
Configurable products present customers with one or more attribute choices to customize the product. In BigCommerce, configurable attributes come in two varieties: variants and modifiers.
Variants
Variants are attributes with pre-determined values. This would include things like size, or color. A merchant sets the available options for the customer to choose from. Variant options can be presented in any of four manners: color swatch, radio select, rectangle label select, dropdown.  To assign variants to similar products, for instance t-shirts, admins can create a "shared" variant. This will apply to all products or categories selected and saves time in generating product variations.

If desired, admins can also:
- Generate unique SKUs for tracking inventory on the variant level
- Set a unique product image for a variant (e.g. show a shirt in chosen color)
- Alter pricing for different variants (e.g. XXL costs more than S)
Single Variant Option (size)
Multiple Variant Options (size, color)
Modifiers
Modifiers give customers a greater depth of customization on a product. A common use case for modifiers would be adding engraving to a product or allowing a customer to add a personalized message or image on a product. Modifier fields come in the following three formats:
Multiple Choice
As with product variants, the customer chooses one from multiple options. Presented as swatches, radios, rectangle list, or dropdown.
Pick List
This allows a customer to choose from a list of products in your catalog. This could be useful in offering add-ons and bundles.
* Note: Only simple, physical products can be used in a pick list.
Other
Additional field types to allow customer input - checkbox, text/number fields, date field, and file upload.
Modifiers can also be associated with price adjustment rules. That is, if a certain modifier is chosen or included (such as custom text), the price may be increased or decreased by a dollar value or percentage; and the shipping weight may be increased or decreased. The product below has been configured to add $5 when a customer elects to include an engraving.