Bernoulli's Principle
Bernoulli's Principle is the idea that fast-moving air pushes less than slow-moving air.
Think of it this way
Hold two flat trays close together and blow air through the gap. The air speeds up in the tight space. Fast air pushes less, so the trays move toward each other. The gap acts like a squeeze point where speed goes up and push goes down.
Explaining bernoulli's principle by grade level
Blow air over a ball and it floats. The fast air you blow pushes less on the ball than the still air around it. The still air pushes the ball back toward the fast stream. That is why the ball stays in place and does not fly away.