In playing with the new Eraser tool, I discovered that there’s actually two totally different ways to use it. The first way is to select any objects that you’d like to erase. Switch to your Eraser tool, and click-drag over the objects, and only the selected object will be erased. The second way is to select nothing and click-drag over any objects and the Eraser will erase the parts of the objects it runs over. To get more “selective” in what gets erased without selecting any objects, you can also Lock objects (Object > Lock > Selection) or Lock Layers and they will remain untouched.
Tip provided by Jeff Witchel, Certified Adobe® Training Provider.