Weight is the force acting on a mass because of gravity. Like all forces it is measured in newtons (N). Weight is calculated with the equation weight = mass × gravitational field strength, or W = m × g. Mass is in kilograms (kg) and gravitational field strength, g, is in newtons per kilogram (N/kg). On Earth g is 10 N/kg, so every kilogram of mass has a weight of 10 N.
For example, a 2 kg bag has a weight of 2 × 10 = 20 N on Earth.
Mass and weight are different. Mass is the amount of matter in a body, and it is constant wherever the body is. Weight depends on the gravitational field strength at the body's location. On the Moon g is smaller, about 1.6 N/kg, so a body has the same mass there but a smaller weight.