The shorter name for Enhanced Traction System used on cars to lower torque to the drive wheels allowing for more traction by using the ABS censors to read the speed of the wheels, if one slips it lowers the torque overall. It has a variety of ways to reduce torque by inhibiting the firing of the spark plug, cutting the amount of fuel to the combustion chamber, and/or up shifting. Also saves on gas a bit but, to me, seems to slow the cars acceleration. I could be wrong.
An engine brake in a semi inhibits the firing of the pistons like the ETS in a car. Fuel cutter is like when hitting the max speed a speed governor will allow, it cuts fuel only the ETS is more subtle. The up shifting should be obvious, it lowers rpm thereby lowering torque.