XLR is a name for a specific style of locking
connector. The term comes from:
X for the series,
L for locking, and
R for rubber insert. In most cases, when someone says XLR cable, they are referring to an audio cable with 3-pin XLR connectors, although the connector is available from two to seven pins. Most
microphones and professional sound equipment have 3-pin XLR connectors, allowing easy
interfacing between devices. Originally invented by
Cannon, (thus sometimes called a "Cannon-plug"), in the 1930's.
XLR.
Xlr-connectors1-300x176.jpg
The predominant manufacturers are
Switchcraft and
Neutrik. For more, see the collaborative Article
Connectors, XLR.