Biscuit joinery requires a specialised tool, but it also provides a quick, simple joint that is strong enough for most applications. Here's how a biscuit joiner works, and a few applications when you might use one.
A biscuit joiner (also sometimes called a plate joiner) works by cutting a slot in two boards, which are then aligned and glued using a small oval piece of wood called, obviously, a biscuit. Like using dowels, biscuits are meant to help keep boards in place while they are glued and clamped.
This video gives a quick demo of how the joiner works, and then shows how it can be used to build simple cabinet boxes. We've talked about other ways to achieve similar results with less expensive tools (like using pocket screws) but if you're getting serious about woodworking, and biscuit joiner is a great tool to have in the workshop.
Biscuit Joinery Tips and Tricks [Fine Woodworking]