Mass is a measure of the amount of matter in an object, typically expressed in units like grams or kilograms. It is a fundamental property of physical objects and does not change regardless of location, whether on Earth or in space. Mass is different from weight, which is the force exerted by gravity on an object. In physics, mass plays a crucial role in understanding concepts like inertia and gravity. An object with greater mass requires more force to change its motion, while gravity pulls objects toward each other based on their masses. This relationship is described by Newton's law of universal gravitation.