If you want to draw attention to something on the slide, you generally go to the screen and use your hands. This is fine if you are in a small conference room. If you are smart, you might carry a laser pointer (which now-a-days comes inbuilt in wireless presenters). You can also move your mouse and take the cursor to any part of the screen. But did you know there was a free inbuilt laser pointer in PowerPoint?
If you want to highlight anything on your screen (in Slide Show mode), you can press Control (CTRL) and then left click on the mouse and move it. Instead of the normal cursor arrow you will see a laser pointer symbol. The laser pointer dot of a wireless presenter is small but this pointer is bigger, hence easier to see.