[soundlight]

DMX is the control protocol for controlling dimmers, moving lights, and dmx accessories for lights such as color scrollers and gobo rotators. The wiki should help here.

When you bring up a fader on a lighting console and the appropriate dimmer comes up, the information link between the console and dimmer that carries the information that tells the dimmer rack what dimmer to bring up is the DMX protocol.

Circuits (the actual thing you plug the light in to) are sometimes on pigtails (those 1' extension cables), sometimes actually on a raceway (big long box with plugs in it that runs the length of a pipe/batten), and sometimes in boxes near the lights, but you need short extension cords to get to them. For some smaller theatres, they do actually run cable from the dimmers, but this is only for low-budget theatres with smaller houses where it's at least semi-practical. These are often semi-permenant but sometimes taken down between shows to re-run elsewhere.