[Koha] Biblio question

Hey all, I noticed when adding a new biblio or editing a present record under catalogue, some of the tags have a '+' sign next to it. When clicked, a small text box opens. Does anyone know: -What exactly those '+' signs mean? -What am I suppose to enter into the textbox provided if I click on the sign? Thanks, Noel Image by FlamingText.com --------------------------------- Need a vacation? Get great deals to amazing places on Yahoo! Travel.