In the Catalog, the Generic brand or the Generic folder is a specific tool that is available to all users across the instance. Every user can use the content in there since it is generic items - it could be brand logos or international fixtures for instance.
It is a cross-brand container and can be linked to a guideline as a normal brand. See how to add a guideline.
You cannot rename or delete this folder. As classic brands, it can only contain folders/subfolders on different levels.