the ECU is the standard computer, but remapped by a tuning workshop/workhouse
they get the std ECU, make some chip changes on the board, then edit the tune
this gives the car more power etc but it can also be risky, as you have no idea what it is tuned for or how safe/unsafe it is
you really should steer clear of remaps and avoid
ie it could be tuned for 800cc injectors for all you know and putting it on a std car could make it go bang
even if you do find your car runs on with a remapped ecu, you can do basically nothing with it, as you cant edit the tune in most cases