Often refers to the 4-pin connectors used to attach DC power to the drives inside a PC cabinet. Molex is a large manufacturer of electronics plugs and sockets that dates back to the 1940s.

On page 4, there is an "IDE Power" connector. It looks a lot like a 4 pin CPU fan connector, but it (obviously) provides different voltages that are appropriate for 3.5" IDE drives (5V, 12V) and ...

NVIDIA's upcoming GeForce RTX 3090 Ti Founders Edition will have a PCIe Gen5 16-pin power connector, replacing the 12-pin Molex MicroFit 3.0 plug that was on the RTX 30 series Founders Edition GPUs.