MASS
Mass is the body of coherent matter. It is the same wherever you are because it is the amount of particles in you. Mass can be measured many different ways, but the best/easiest way is to use grams. Grams are the easiest because they can be measured using many different devices. We use grams or kilograms as a metric unit to label mass. The SI unit for mass is kilograms and the symbol is kg.
WEIGHT
Weight is your mass multiplied by the gravitational pull of the planet you are on. That is also how you can calculate it. You multiply your mass on a planet by the gravitational pull of that planet. You can use a scale to measure weight. A scale works as you step on it, the plates inside rotate to the appropriate amount. In the USA, we use the pounds to label weight. The metric unit we use to label weight is grams.
GRAVITY AND OTHER PLANETS
Gravity is the force attracting bodies to the Earth's center. Gravity depends on the distance and size of two masses. The average gravitational pull of earth is your weight, multiplied by 1 kg, and that is divided by 2.205 pounds (that is 1 kg). The gravity of the planet your on increases or decreases depending on the size of the planet. If you are on Jupiter, it is likely to have a very strong pull f gravity. The moon is smaller and has a less pull of gravity which is why we can float on it. As the pull of gravity increases your weight increases with it and it decreases as gravity decreases. Mass does not change no matter where you are. Mass is the amount of particles inside of you and it never changes.