Discogs is a largest online database of information about audio recordings. I use it daily as a music librarian during the cataloging of CDs and vinyles, to help me decide in which genre to put the disc, to check the publisher of the disc, and just to get more information about the artist. I love it! There is often information about some obscure artist or disc, and it really helps in organizing information. I know that there is a marketplace where people can buy discs, and probably many more interesting services, but I didn't have time or need to explore them for now. Just information seeking is enough for me.
I saved sooooo much time with with this database while cataloging! Thank you Discogs! :)