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I usually explain what dmx is this way:

imagine puppets, the kind with strings (marionettes). Each string represents a data channel or address. Typically, a control console has 512 channels (strings), or multiple sets of 512 channels (universes). You as the puppet master control each string and as you raise and lower the fader, twiddle the knob, press the preset, etc., it raises and lowers the string, and makes the puppet do what it's supposed to. The difference is that dmx is done with electrons, not actual string. The other difference is that instead of raising an arm on a puppet, you're sending commands to a fixture and the microprocessor in the fixture (even dimmer racks have them) translates that into some mechanical action (activating a dimmer, spinning a color wheel, etc.).