There are songwriter's fees and publishers fees. When you write a song you own 100% of both. What publishers do is push your songs to artists, films, TV etc. You, or they, don't earn a penny if the song never gets used. A lot of people don't have the time, knowledge, or connections to be their own publisher. When you are first starting, it is very common to give up 100% of the publishing to someone you believe can get your song signed. Once you get a name as a songwriter you can bargain for percentages. There is a lot more involved in this and the best way to learn is to read. Jason Blume had a good one called "The Business Of Songwriting". I read it a couple of times and it gives you a pretty good handle on how everything works.

Have a goodun,

John W. Selleck BMI Songwriter
A day without learning is a day lost forever.

www.soundclick.com/johnsings
www.soundclick.com/johnwselleck
www.soundclick.com/johnselleck
https://www.soundclick.com/artist/default.cfm?bandID=1468958 For Selleck/Kay co-writes