MC4 connectors, named after their original manufacturer Multi-Contact are used mainly for connection of solar panels to inverters.
Typically the panel positive output lead will be fitted with a male MC4 connector, the negative connection will be via a female MC4.
However, the terminology can be confusing as a male connector, has a ‘male’ plastic insulator together with a female metal contact.
The female connector has a female plastic housing, containing a ‘male’ metal contact.