In the past, it was widely used to connect hubs and switches to each other to maintain the built-in crossover that would have been reversed if connected with a regular cable. Ports in modern hubs ...

The image above is not of a full male-to-male cable, only the ground is connected, and the generator is not running. We all know Ethernet has the crossover cable, cars have jumper cables ...

Referred to as "auto MDI/MDI-X," "universal cable recognition" and "auto sensing," it eliminates having separate MDI and MDI-X ports, selector switches and special crossover cables on the equipment.