A switch is a small control for an electrical device which you use to turn the device on or off.

If you switch to something different, for example to a different system, task, or subject of conversation, you change to it from what you were doing or saying before.

If you switch your attention from one thing to another or if your attention switches, you stop paying attention to the first thing and start paying attention to the second.

If you switch two things, you replace one with the other.