Matchmaker is a structure of puzzle, first introduced by Serkan Yürekli (Turkey) in the 4th OAPC (2009).
In this structure, several puzzle rules that use similar notations and several puzzle grids are given. There may be some extra rules or extra grids. You have to match each grid with rules so that each grid has a solution. It is possible that there are multiple rules with which a solution exists in one particular grid, but there is only one complete combination.
First Matchmaker puzzle from the 4th OAPC can be seen here). It used 5 rules and 4 grids. Rules were: Islands (Nurikabe), Masyu, Minesweeper, Top Heavy and Tapa. Additional rules; In Nurikabe, multiple numbers being within one region is allowed. In Minesweeper, there will be 12 mines. In Masyu, odd numbers are the black circles and vice versa. This example is from OAPC IB.