GarageBand is a multitrack (you can record one instrument at a time) recording application that contains a complete collection of audio tools for experienced recording veterans and novices alike. You can record real audio pieces, play with software instruments, create parts using Apple Loops, add effects, mix your music and play it all back with iTunes or include in your iMovies.
It is an easy to use but powerful recording tool for musicians, podcasters, presenters, students or anyone that wants professional sounding audio that can also be embedded. Using the Inspector audio can be embedded into websites, keynote presentations, pages documents and imovie. Some blogging platfroms even allow you to embed mp3 files. I have had kids making there own compositions in under 5 minutes.