What is ECU (Engine Control Unit) for the Honda Civic?

Sounds to me like they have reflashed the ecu back to a factory, basically think of the ecu like a computer, it has a map (or rom) of how to run your engine, if for some reason the map in the ecu gets corrupt the ecu doesn't know how to run the engine properly, so to fix it they remap your ecu, eg they replace the map of how to run the engine,