The smallest unit of permissions that can be granted to a user in Business Manager (B2C Commerce)

When editing the roles assigned to a user in Business Manager under [Administration > Organization > Roles & Permissions > {Role ID}], the smallest unit of permissions that can be granted in the [Business Manager Modules] tab is a module. 

For example, if read/write permissions are granted for the [Products and Catalogs > Products] module, the user will be able to view and edit all information under [Merchant Tools > Products and Catalogs > Products] in Business Manager. 

Permissions cannot be controlled on a per-tab basis within the product detail screen such as variations tab.