widgets are like little apps that are always running in the background. they each take up a small portion of screen space, and ALL of them are brought up with the press of a single key, regardless of what you're doing, and all of them disappear with another short action. (so with one keypress you can bring up 20 widgets) they're very good for quick references and tools like calendar, calculator, weather report etc.
Much less obtrusive than having to switch to another app or several apps while you're in the middle of something.
