Okay kiddo, so imagine you're playing a game where you have to protect yourself from something that might hurt you, like a ball. A high risk modular tactical vest is like special armor that grown-up soldiers wear to protect themselves from things that might hurt them when they're fighting in a war.
It's called "modular" because it's made up of different pieces that can be taken off and put back on depending on what the soldier needs. Think of it like Lego blocks that you can move around to make different things.
Some of the pieces might be really strong and hard, to stop bullets or shrapnel from explosives. Others might be softer, to cushion the impact of something hitting the soldier.
The vest is also "high risk" because the soldiers who wear it might be in very dangerous situations, where bad guys are shooting at them or there might be bombs going off. So they need to wear something that can protect them as much as possible.
Does that make sense, kiddo?