What is Transistor Controlled Ignition?

Instead of using a distributor to determine when each cylinder fires, the car's ECU uses camshaft and crankshaft position sensors, along with MAP/MAF and throttle position sensors to determine the optimum time to fire each cylinder for the most power/lowest emissions. As opposed to fixed advance (vacuum or centrifugal) employed in distributors. Transistor Controlled Ignition is commonly referred to as Coil On Plug (COP), Transistor Controlled Ignition is just marketing bumpf to make it sound awesome.