This is the process wherein you would be playing a short portion of the song in order to introduce it to other people. Take note that fanfare is usually more appropriate when certain brass instruments are used. For example, you may use a trumpet in order to play a certain song.
The word fanfare may have different meanings when you use it in other ways. For example, some use the word fanfare to signify that they are going to make an important announcement. There are also some who use this to show a great interest in something.