Inclined Plane
Inclined Plane is a flat surface set at an angle that makes it easier to move heavy things up or down.
Think of it this way
A ramp is just a flat board leaning against a step or raised surface. You slide a heavy box up the ramp instead of lifting it straight up. The ramp spreads the work over a longer path. Less force is needed because the distance is greater.
Explaining inclined plane by grade level
Think about pushing a heavy box up a ramp. It takes less work than lifting the box straight up. The ramp is long, so you push a longer way. But your push feels much lighter each step.