they exploit your copyrights... in a good way. they own the copyright to the song. they distribute the CDs pretty much. most publishing money is made from mechanical royalties (every time the CD is recreated in a tangible medium) and performance income (every time its played on the radio or broadcast on TV). the publisher then pays the artist their percentage. 8.2 cents right now for each CD mechanicaly reproduced. there is also synchronization income which is payed whenever your song is "synched" with moving film... like on a movie or something. honestly, copyrights and publishing could take up a 100 page thread... easily. its one of the most complicated and exhausting topics. you really need to get a book and read up on these things. i HIGHLY recomend buying "the muscians business and legal guide". its not too expensive and its written by very reputable attorneys. it will answer all the questions you could ever have about the biz. every musician who plans to make a life out of playing should read it, or a book like it. knowledge is power, especially in this industry.