A good eraser (not smudging!) is an almost indispensable drawing tool. It’s only super annoying if your paper suddenly folds or tears while erasing. I have seen it happen quite often. Therefore, keep your paper taut with your other hand while you erase. You then erase in the area between your thumb and index finger.
Exercise 1: draw a figure somewhere on your paper and erase it in the manner shown here.
With a good eraser you can draw light in the dark, change shadows and lighten lines. See the examples below. This works best if you use soft pencils (2B, 3B, etc.). On larger formats and when using charcoal, a special kneadable eraser is more useful.
Exercise 2: draw figures like the ones below and change (part of) the outlines or shadows with your eraser.
You can clean a dirty eraser with sandpaper.