Type A - Male QD/ Female 1/2" NPT. The most common use for this part is attaching to the wort in/out ports on a plate chiller. It can also be used for recirculation ports, the in/out of a HERMS coil. etc.
Brewhardware's stainless steel Camlock style disconnects (sometimes called cam and groove) are a great compromise between cost and function for making and breaking connections between your vessels, chillers, pumps and hose sets.
The "quick disconnect" portion of the camlock system consists of male and female parts. The male side is a cylinder with an external concave recess around the circumference and a front sealing face. Once inserted into the female coupling, a set of cammed arms are drawn back to apply pressure to the male's recess which locks the parts together and holds the male's sealing face tight to the captured gasket.
It's most common to use the male part on fixed brewery components while the female coupling end is typically installed on the more mobile parts like hose sets.