Weight is the measure of the gravitational force on an object. Weight is related to mass but is actually a separate property. Weight and mass are often treated as interchangeable because gravity on Earth does not vary much based on location.
Mass is a direct measurement of the amount of matter present in a object. The only way the mass of an object can change is if matter is added or removed. Weight is calculated by multiplying the mass of an object by the acceleration due to gravity. This acceleration differs based upon where the object is in the universe.