A limit switch is a device that activates or modifies a control function when a moving part reaches a predetermined position. It can be mechanical, using an arm that is triggered when compressed, or optical, where a flag interrupts a light beam to signal the switch. Limit switches are essential in systems driven by motors, as they indicate when the motion range has been reached, preventing damage. They are commonly found in various electro-mechanical mechanisms and are often integrated with software for monitoring. Understanding limit switches is crucial for managing equipment that involves significant movement.