Audio plugs are available in several sizes and varieties like jack plugs, cinch plugs and XLR plugs.
Most common is the mini-jack plug, measuring 3,5 mm (1/8″) or 2.5 mm. Suitable for low voltage signals, jack plugs find their uses in earphones, sound cards and the like. They exist in mono (signal and ground) and stereo versions (signal left, signal right, and ground) and mobile phone applications use a version with four connections (signal left, signal right, microphone, and ground).
Cinch plugs are used on stereo’s, whereas 1/4″ (6.35 mm) jack plugs are used in musical instruments and professional musical equipment. XLR plugs can be found on professional portable audio equipment because they are quite robust.
Warning. Do not to use male jack plugs for supplying electrical power, since they tend to short circuit when you insert them, especially when the counter plug or chassis part has a metal housing. User a dedicate plug like the power socket instead.