Okay kiddo, so an assault pioneer is like a really important person in the army who helps make sure that the soldiers have everything they need to fight and be safe.
They help with digging, building, and setting up all kinds of things like bunkers, bridges, and obstacles to keep the enemy from getting through. They also help clear out areas that might be dangerous, like mines or booby traps.
In addition to all of that, assault pioneers also have special training in fighting and defending themselves in close combat situations. So they're like super skilled fighters too!
Overall, assault pioneers are really smart and tough and help keep the military safe and strong. Pretty cool, huh?