The throttle is the actual valve, a piece of metal sitting inside the air intake that rotates to allow various amounts of air to pass into the engine.

That thing, the valve, is still properly called a throttle on all IC engines. And even the very modern computerized gas engines have one.

In older direct fuel injection, the accelerator pedal was still directly connected to the throttle valve. A separate fuel injection control system increased and decreased the amount of fuel going in to maintain a steady fuel-air ratio.

On modern automobiles, the pedal is usually fully "fly-by-wire". The computer reads the pedal position like a joystick and decides how to move the throttle and fuel injection to achieve the commander input.

Electric cars are built around brushless DC motors. The "DC" there is a bit of a misnomer. These motors rely on a microprocessor to generate the variable-frequency AC waveforms to drive the stators in real time. This allows higher efficiency than older motor control technology, but it means that there's basically no way to operate the motor without the motor control software. So in these cars the pedal is always just a joystick input.