The DMX protocol itself sends a range of values on one or more channels. 

DMX does have 512 channels, named a universe, and on every channel, 255 values can be sent. 

As DMX is a digital protocol, receiving devices can be daisy-chained as the addressing is done at the devices. 

Every receiving DMX device constantly listens to all channels but only makes use of a few settable determined numbers of channels. 

What a value on a channel means for the receiving device depends on the device itself, and if the device has been set to use that channel and value. 

e.g. If a device like an RGB lighting PAR does use 3 channels (every channel controls one color like RED, GREEN, BLUE) and the value 0 means 0% brightness 

and the value 255 means 100% brightness of the color, and it uses the start channel 5, then a command on the DMX channel 6 with value 255, 

send on the DMX universe, makes this LED PAR light up the green light with full brightness (100%).