Edge jointing or just jointing is the process of making the edge of a wooden board straight and true in preparation for subsequent operations, often ultimately leading to joining two or more components together.
Normally, the desired outcome of jointing is an edge which is straight along its length and perpendicular to the face of the board.
However, there is another technique often used when gluing up panels, referred to as a sprung joint.
[1] In this technique, the desired outcome is an edge which is slightly concave along its length.
When two such edges are brought together and clamped, the sprung edges create greater tension at the ends of the join, which assists in creating a seamless joint.