3-pin XLR
3-pin XLR connectors are mainly used for balanced audio signals. Using a balanced signal reduces the risk of inference.
There are a number of different XLR's - 3-pin, 4-pin, 5-pin etc
3-pin XLR Male
3-pin XLR Female
¼" Jack (6.5mm Jack)
There are two types of 6.5mm Jacks: Mono and stereo. The mono jack has a tip and a sleeve, the stereo jack has ring, a tip and a sleeve.
Jacks also come in various sizes - 6.5mm (¼"), 3.5mm, 2.5mm. The wiring for all of them is the same.
1/4" Mono Jack
1/4" Stereo Jack
RCA
RCAs are used a lot for home stereos, videos, DVDs etc.
The RCA can carry either audio or video. It is wired the same way as a mono jack: The center pin is the +ve, and the outer ring is the -ve or shield.
RCA Male
Audio Connectors
There are a variety of different audio connectors available.
The most common types are 3-pin XLR, RCA, and 6.5mm jacks (also known as ¼" jacks)