Starters.

A reversing starter is used if the motor must be able to run in both directions. It can be implemented by several methods.

Star-delta starters remain popular in some parts of the world, but they have a few problems that have been aired many times on CR4 threads.

In addition to Tornado's comment, these are also helpful:

Forward reversing starter: It is required where the motor need to rotate in both direction such as the MOV (Motor Operated Valve). MOV is used to close or open the valve operated by motor. In this case, motor rotates in one direction for opening the valve and opposite direction for closing the valve.

Star Delta Starter: It is required where the motor starting current needs to be reduced (approximately 1/3rd) and the initial starting torque of the load is less (approximately 1/3rd).

- MS

Read your textbook. This sounds like a homework question.