What is a screensaver

Everytime I ask what is a screensaver in a dash cam, I get results like "how to set up a screensaver", "has anyone accidentally left their screensaver on?" stuff like that, but I don't know what it even is.

I have a dashcam, and while I was trying to remove the camera off the window, I found myself in the "screensaver" thing. I don't know if I turned it in or if it was already at 3 minutes, but I want to figure out what a screensaver is so that I know whether to turn it off or not.