This article is from the Bagpipe FAQ, by Denise McNickle email@example.com with numerous contributions by others.
...I keep hearing about
practice sets, half sets, full sets and so on. What are the differences and
which do I need to get started?
A practice set consists of a bag, bellows, and chanter, and is all you
really need to get started. A half set consists of the practice set plus the
drones, and is also reasonable for beginning players though you'll find that
you won't actually use the drones for quite some time. A full set consists of
the half set plus regulators. If you're just starting out on the pipes then it
may be a matter of years before you're comfortable enough to manipulate the
entire full set.