3 pin/4 pin fan connecter is used to connect processor fan with the motherboard.
Processor Fan:A computer fan is any fan inside, or attached to, a computer case used for active cooling, and may refer to fans that draw cooler air into the case from the outside, expel warm air from inside, or move air across a heat sink to cool a particular component. Generally these are found in axial and sometimes centrifugal forms. The former is sometimes called a "electric" fan, after the Rotron Vertical line, while the latter may be called a "biscuit blower" in some product literature.
Motherboard CPU Fan 4 Pin header Connector:
| pin | name | color |
| 1 | GND | Black |
| 2 | +12v dc | yellow |
| 3 | sense | green |
| 4 | control | blue |
| pin | name | color |
| 1 | GND | Black |
| 2 | +12v dc | red |
| 3 | sense | yellow |
| 4 | control | blue |
