Gravity refers to the phenomena that causes all the bodies to attract one another. Thus is also the reason why we fall back to earth when we jump or why all the fruits fall down from plants. The attraction of bodies for each other is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Motion refers to the movement if a body. A body is said to be in motion, if it is moving.
Force is, typically, a push or pull acting upon a body and depending on its magnitude will cause a change in the motion of an object. According to Newton's second law of motion, the force acting on a body is the product of its mass and acceleration. The first law of motion states that a body at rest or in motion will continue to stay in same state until and unless an external force is applied to it.
Gravity is a force, acting downwards on earth, and causes motion by making us fall down when wejump.
Hope this helps.