Friction can also produce motion, as in the case of walking. Usually heat is produced as a result of friction. Some surfaces are more difficult to move objects over. Examples include dragging a box across a carpet Vs a smooth floor. Gravity is a force of attraction that pulls objects toward the earth.
Gravity is the force that keeps the earth in orbit about our sun.
We are closer to the earth than the sun, so we are pulled toward the earth more strongly than toward the sun. Gravity between most ordinary objects is too weak a force to notice. Students will observe that more washers are necessary to change the motion of two books than one book. This is easy to explain in terms of inertia and the increased friction due to increased weight. The more massive an object the greater the force needed to change its motion.