Weight and mass are two important concepts in physics. Mass refers to the amount of matter in an object, measured in units like kilograms or grams. It remains constant regardless of location. For example, a 5-kilogram bag of flour has the same mass whether on Earth or the Moon. Weight, on the other hand, is the force exerted by gravity on an object. It is calculated by multiplying mass by the acceleration due to gravity. Therefore, the same 5-kilogram bag of flour weighs about 49 newtons on Earth but only about 17 newtons on the Moon, where gravity is weaker.