A practice chanter is an instrument in its own right, but its primary purpose is to provide a bridge to playing the Highland bagpipe. Later on it provides a convenient way to practice new tunes, complex fingerings, and so on, especially at times when practicing on a full pipe is impractical. Though quiet, it does require a moderate amount of air pressure and thus helps get the fledgling piper into shape for a full set. Silence between notes is of course available, so one can position fingers, think about things, etc. There are several good ones, none of which presume any prior knowledge of pipes, or for that matter music.
Some tutors have optional accompanying audio tapes or CDs that can be most useful.
There are also tutors for more advanced students and there are also some teaching videos available. At some point, perhaps in several months or so, the lessons in the beginning tutor are mastered and the piper can play the practice chanter with confidence for a good long time - say half an hour. Then he or she is ready to approach a bagpipe proper. Having mastered that, the chanter might next be stopped off and one drone activated, then two, then three. Or, one drone might be added to the chanter.