Mass - the amount of matter in an object. Mass can also be defined as a measure of the inertia of an object. The mass of an object is constant. Mass does not change as an object is moved from one place to another. Weight - a measure of the pull of gravity on an object.
All objects exert a gravitational attraction on other objects.
Gravity is the weakest of the natural forces. The greater the mass of an object, the greater the gravitational force. The pull of gravity between objects decreases as the distance between the centers of the objects increases. For this reason, the weight of an object is not constant. However, an object orbiting the earth is not weightless.