Can someone explain...............

When you stage a tree you light the first bulb "pre stage" then you pull a little forward and light the second bulb "staged". If you pull a little more forward the first bulb will go out. "Deep staged"

Pretty much you will shorten the amount of time between your reaction and breaking the light.

You are more likely to red light and some races don't allow it. But, you can gain a slight edge if you are very consistent.