A music publishing agreement is created between the songwriter(s) and the music publisher. The agreement covers all the aspects of the copyrights of the music composition. In this process, the publishing company will find users for the music piece and sell them a license in order for them to use the song. The money they earn from these licenses is collected and given a part to the songwriter.
The songwriter should agree on giving a part of the revenue they generate from the song to the publisher along with a portion of the copyright.
In publishing administration agreements, on the other hand, the songwriter doesn’t have to sign over a portion of the copyright and the songwriters will simply allow their work to be published by the administrator for a time period that they have agreed on.