A wagon with large wheels is easier to push over rough ground than is a
wagon with small wheels. As we move the wagon forwards it also
moves up and down. A large wheel doesn't reach the bottoms of
the valleys, and spreads out the effects of a bump over a
large horizontal motion. A small wheel has to move from
valley to peak as it moves forwards a small distance.
Effectively, the large wheels only encounter small inclines,
while the bumps are much steeper for the small wheels.
One way we meet this effect is in trying to roll a loaded cart over a power cord. The entire energy needed to lift the cart must be supplied in a small forwards motion; the force that needs to be applied can be larger that the weight of the cart!
An inclined plane is a way to raise a heavy object without exerting a large force. Its secret is that we spread out the effort of lifting: we don't push as hard, but move the object much farther.
The threads
on a bolt are also an inclined plane, of sorts. As we move the wrench
a large distance, the nut advances a small distance; the force we
exert is relatively small, while the nut is being pulled along the bolt
with an enormous force.