Hi! It’s been a while, eh? But Caleb had a fencing tournament on Monday, and I was able to borrow a little camera with video capability to record for posterity. (Caleb is on the left.)
This is called foil fencing. The silver vests they are wearing are called lamé, and they’re connected to a scoring box, which you can see on the floor to the right of the fencers.
The tip of the foil must be depressed while in contact with the lamé to cause the scoring box to beep in your favor with a red or green light. If the tip is depressed for any other reason — touching an arm, or the floor — the beep has an indicating white light.
But there are also rules about right of way, so you can score only if you were the fencer who began the attack.
You can read more here at Wikipedia.
And he won second place!