There is no Yate database. You can create an endless number of databases for your own use. I have a maintained track and album database as well as an artist database and a database of my recent purchases.

When you export metadata via a File>Export or the equivalent action statement any field which maps to binary data other than an artwork item is exported as a .yateblob file. Typically this is ID3 Private Information or General Encapsulated Object items. Basically it's unknown binary data which can be restored. While yateblob doesn't really mean anything, no well know extension would make sense.