This adapter will enable you to use a mouse with a 6 pin Mini-DIN (PS/2) connector to a computer with a 9 pin D-SUB (Serial) connector.
This requires that the mouse handles both protocols. A mouse like this is sometimes referred to as a combo-mouse.
(To the computer)
6 PIN MINI-DIN FEMALE to the mouse.
9 PIN D-SUB FEMALE to the computer.