Essentially, GarageBand is a portable recording studio, enabling the user to record via the inbuilt microphone and sequence together their own music using a variety of "smart instruments" such as piano, drums, guitars, basses and strings, as well as pre-existing "apple loops" of various styles. You can even plug a guitar directly into your iPad via a USB camera connection kit and use virtual guitar amplifiers to emulate the experience of a genuine recording session.
Although it could never be an alternative for real instrument performance, it is a useful way of jotting down musical ideas, encouraging creative composition for a beginner, and getting young people enthused about and engaged with music-making.
Download GarageBand here