The mass of an object creates a force field around itself. Any other mass is attracted towards that object. The force field around a mass is called a gravitational field.Any two masses will attract each other with an equal and opposite force.If a small 'test' mass is placed close to a massive body, the small mass and large mass will attract each other with an equal and opposite force, but this force is too small to move the massive body, although the small mass will move if it is free to do so.