A plane surface set at an acute angle to a horizontal surface, a direction of motion, or a direction of force. Inclined planes are used to increase the distance over which work is done, reducing the amount of force needed to impart energy to a system. Examples are ramps, sloping roads, chisels, hatchets, plows, air hammers, carpenter's planes. Rolling a stong rock up a hill, requires less force than lifting it straight up off the ground.
A wagon team on a steep hill would traverse back and forth to reduce the gradient experienced pulling a heavily loaded wagon. This same technique is used today in highways that travel through mountains.
Big Thing here is friction.