Integrated Ignition Control System
The brain of most modern furnace electronic ignition systems uses an integrated circuit board to control many sophisticated processes. These integrated controllers can also perform self-diagnostics providing codes similar to the diagnostic computer in your car. The integrated circuits continuously monitor the furnace's operation and the operation of the integrated control module itself. If a failure occurs, LED's can indicate a failure code. The codes are listed in the Owner's manual and also likely on the furnace door.
You will often find the control board in the blower compartment of the furnace with a 3-5 Amp fuse to protect the board from a short.
These integrated controllers are always used on higher efficiency furnaces that rely on many sophisticated design features to reach their high AFUE ratings of over 90%. However, they still provide the same basic function as their less intelligent cousin, the non-integrated electronic control module. That is, to control sequences of operation for the furnace.