Your mass is how much of you there is; your weight is how hard gravity pulls on it. $W = mg$ — W equals m g — puts numbers on that: $W$ is the weight in newtons, $m$ is the mass in kilograms, and $g$ is gravity's acceleration, $9.8\ \mathrm{m/s^2}$ on this paper. Every kilogram gets charged 9.8 newtons, no exceptions, like a tax. On the Moon the same kilograms would be charged less; the stuff itself never changes.

The exam wound this lesson exists to prevent: quoting the mass number as the weight. A 10 kg crate does not weigh “10” — it weighs 98 N. The bathroom scale is a cheerful liar here: it FEELS force and prints kilograms, quietly dividing by 9.8 on your behalf. In this room, nobody divides on your behalf.