Mass and weight
What is the difference between mass and weight?
It might be better to say that mass is the amount of "stuff" inside an object measured in kilograms. While increasing the size of an object can increase its mass, two objects of the same size can have different masses, depending on their density. To understand the difference between weight and mass, think about traveling to different planets. On each new planet, your weight (measured in Newtons) will be different because the gravitational force is different, but your mass will always be the same (provided you don't go to the bathroom or get a haircut).