Mass: how much matter is in an object.
We measure mass by weighing, but Weight and Mass are not really the same thing.
The most common measurements:
Grams are written as g (for short), so
250 g = 250 grams
1 kilogram = 1,000 grams
Kilograms are written as kg (a “k” for “kilo” and a “g” for “gram), so
10 kg = 10 kilograms
1 tonne = 1,000 kilograms
Tonnes are written as t (for short), so
5 t = 5 tonnes