The force with which a body is pulled towards the earth is called its weight. If m is the mass of the body, then its weight W is given by
W = mg
Since weight is a force, its unit is newton. If your mass is 50 kg, your weight would be 50 kg × 9.8 ms–2 = 490 N.
Since g varies from place to place, weight of a body also changes from place to place. The weight is maximum at the poles and minimum at the equator. This is because the radius of the earth is minimum at the poles and maximum at the equator. The weight decreases when you go to higher altitudes or inside the earth.
The mass of a body, however, does not change. Mass is an intrinsic property of a body. Therefore, it stays constant wherever the body may be situated.