Is the BalloonItemizedOverlay a library?

[fahimeh hashemian]

I am a beginner android programming.I want to create a balloon on the map. I read mapViewBalloon-example on this link LINK but i don't know, is the BalloonItemizedOverlay a library?? Should i add it to the program or i should write BalloonItemizedOverlay class in the program? The BalloonItemizedOverlay like another libraries of android like android.content.Context? I read this class but i could not understand most of the code of this class

Thanks for help