Molex is the name of the company who develops computer and other related connectors and products. This term is also known as the Molex power connector, which is the connector shown in the picture and is what connects your computer power supply to drives and devices inside the computer.
What devices use a molex connector?
Almost all devices inside your computer use a molex connector. Below are the common devices that connect to a molex connector.
Below is a diagram of this connector with its four connectors as well an explanation about each of the pins.