Weight is the force exerted on an object due to gravity. It's a measure of how strongly gravity pulls on an object.

The amount of substance in something is called its mass. Mass is a fundamental property of matter, representing the amount of matter an object contains.

Here's the key difference:

* Weight is affected by gravity. You would weigh less on the moon than on Earth because the moon's gravity is weaker.

* Mass remains constant regardless of location or gravitational force.

Think of it this way:

* Mass is like the amount of "stuff" in an object, like the number of atoms in it.

* Weight is how heavy that "stuff" feels due to gravity.