The moon is about 1/4 the size of Earth, and has much lower gravity, about 1/6 of the Earth. Since "weight" is actually a measurement of the gravitational pull on an object, your weight on the moon would be 1/6 what it is on Earth. Your mass (amount of matter that makes up you) of course still stays the same, so once you return to the Earth, your weight will be normal again. You may wish to avoid Jupiter, however, where you would be 2.4 times heavier.