Mass is a measurement of the amount of inertia an object has, or in other words, a measure of the resistance to a change in motion. The mass of an object is the same anywhere.
Weight is the measurement of the force of attraction between two bodies.
The weight of an object varies according to where the object is. We usually think of the weight of objects on Earth, but you can also think of weight on the Moon or on Mars. The planets would follow a straight line tangent to the circle defining their previous path. The sun's gravitational force provides the centripetal acceleration necessary for their nearly circular orbits. The net force on a cart pulled to the left with a force of 100N and to the right with a force of 30N is 70N to the left.