Mortise and tenon
Mortise and tenon joint is the method of joining timber by working a solid rectangular projection in the one piece and cutting a corresponding cavity to receive it in the adjoining piece. The projection is called the tenon, and the cavity the mortise. Joints of this type are secured in various ways.
Simple and strong, the mortise and tenon joint has been used for thousands of years by woodworkers around the world to join pieces of wood, usually when the pieces are at an angle close to 90°. Although there are many variations on the theme, the basic idea is that the end of one of the members is inserted into a hole cut in the other member. The end of the first member is called the tenon, and it is usually narrowed with respect to the rest of the piece. The hole in the second member is called the mortise. The joint may be glued, pinned, or wedged to lock it in place.
This Mortise and tenon introduction is partly based on a wikipedia article.