The tonne is a unit of mass (acceptable for use as weight on Earth) and is a non-SI metric unit. It has the symbol t.
1 tonne is equal to 1000 kg. In the US it is called a metric ton (to avoid confusion with other similarly named units like the short ton, the long ton and the register ton. It is equal to approximately 2204.6 lbs.
Tonne is the correct spelling in England and France although ton is acceptable across the world. Before the establishment as an SI-derivative (or metrication), the ton (or imperial ton) was equal to 2240 avoirdupois pounds (or 20 hundredweight). This is only 16 kg different from the up to date (metric) tonne as we know it today.
A car weighs about a tonne.
The gram is a unit of mass (acceptable for use as weight on Earth) and is a multiple of an SI base unit with the symbol g.
Although without a prefix, it actually represents 1/1000 kg. It is the first subdivision of the SI base unit; kilogram and 100 g equals 3.527396195 ounces.
It is the most common unit for measuring ingredients (except liquid) in cooking and purchasing food goods in the world today.
The majority of nutritional values and information is expressed in terms of 'per 100g'.
1 g is roughly equal to the weight of bank note or a pinch of salt.