By definition, Assets are all entities that exist independent from Products. Or, in other words, a Product is created from Assets.
Assets are taken from two Databases: the Support DB and the Project DB. You can use the Assets from the Support DB, but are not allowed to modify them.
This Page gives an overview about the currently available Assets in both Support and Project DB.
The Asset categories are:
Commercial Assets: Products, Properties, Property Values
Geometry Assets: Geometries and Layers
Material Assets: Parameters, Mapping, Textures, etc.
Image Assets, for the Projection Modes (Only available if 2D is installed)