Custom Parameters allow you to build User Interface with the same widgets TD itself uses. This allows you to quickly pick out the parameters of a network that you want to interactivly control for example through MIDI, OSC, DMX or by a users interaction with a kinect. You can copy paste them between components and most Preset systems rely on them.
Use a Parameter CHOP to collect Custom Parameters values from the parent (per default) or from anywhere else in your network.
Use a Parameter COMP to turn Custom Parameter pages into interactive Panel Objects for Perform Mode.