Catalogs are just a way to divide your music selections in music, videos, karaoke and live so that you can enable or enable them however you like.
For example, most karaoke DJ's will also take requests for plain music so the host can opt to have the user select from either catalog during the search.
Another example is that live acts will NOT take requests for any other than their live music catalog.
Selecting only one catalog will disable the catalog selection so the user is only able to search that 1 catalog.
