What does the TPS sensor do?

Answer 1

Throttle Position Sensor (TPS), it detects how open the throttle body plate is to govern how much fuel is delivered to the engine. One of the myriad of inputs your engine control module uses to control your engine.

If you are getting a fault code due to the TPS, try cleaning the throttle body out with a spray of throttle body cleaner (not carb cleaner) carbon buildup can cause it to stick. If it does stick open, some vehicles will default to "limp mode" to keep them from accelerating uncontrollably.