A P-DMX controller is one that accepts DC power and DMX on the same CAT5 cable. It in turn drives pixels, DC output, servos or other display items.
Each P-DMX controller takes the 24-48V DC power and converts it down to one or more lower voltages. It may simply convert it to 5V only to power 5V pixels as well as the electronics that drives them. Alternatively, it may convert it to 12V for RGB strip as well as 5V (and/or 3.3V) for the drive electronics.
The block diagram below shows an example P-DMX Pixel Controller.