Power Steering Pump
The power steering pump is powered by the engine's fan belt. It spins vanes inside a chamber and forces hydraulic fluid through lines down to a steering box that converts that hydraulic pressure back into a mechanical movement (the tie rods moving from side to side) to move the wheel hubs. This moves the wheels together.
Tie rods are steel rods that move from side to side and force the front wheel hubs to move with them. They get their input from the steering box that's connected to the steering wheel. The steering box is usually power assisted so that the forces required to steer the car is easier.