You mean like files?
An asset is just a fancy word for a file, but used by creatives to describe a visual/audio/video file.
Canto supports 99% of all assets. The most common file types are PDF, PSD, AI, INDD, TIFF, EPS, PNG, JPEG, MPEG, MP4, MOV, AVI.
Canto can pull metadata from most files and even implement that data into some of its features, like Digital Rights Management.