A powerbar is a special type of snack that can give you lots of energy! It's like a candy bar, but instead of just being full of sugar and chocolate, it also has things that your body needs to keep going, like protein and carbohydrates.
So when you eat a powerbar, it gives you a little bit of energy right away from the sugar and chocolate, but it also gives you longer-lasting energy from the other things in the bar. That way, you can keep running around and playing without getting tired too quickly.
It's kind of like if you had a special potion in a video game that gave you lots of extra strength and energy to keep fighting the bad guys. But instead of a potion, you can just eat a powerbar!