Probably the EEC (Electronic Engine Control) or PCM (Powertrain Control Module. Ours is actually an EEC IV, newer Fords have the EEC V. It is the computer that controls the engine and other functions. It it located behind the passenger side kick panel up near the glovebox. It is in the same place on all 'Birds.
You probably also hear OBDI or OBDII in conjuntion with the EEC. That is the On-board Diagnostics version 1 or 2. All SCs have OBDI.