A performing rights organization, or P.R.O., ensures that songwriters and publishers receive payment for use of their music. They do this my collecting royalties for your music.
When a song is played in public, like on any kind of radio (AM/FM, streaming, or satellite), in a venue, or TV shows and commercials, it is required that they pay for the use.
The P.R.O. collects those payments, and distributes them to the rights holders. You must be registered with a P.R.O. such as ASCAP, BMI, or SESAC to receive these services.