A discrete code is a code that is hidden, that can do certain things on your device. For instance, most devices come with 1 button that cycles a device on/off. Using discrete codes, you can set up your remote to have a separate "On"(as well as "Off") button, that will only turn the device on and not off, if pressed again. This is nice for macro programming, as, if you have the macro turn many things on at once. If something doesn't get turned on the first macro button push, you can redo the macro again, without fear of having everything that turned on, the first time, turn off.