Original: Crabs are found in all of the world's oceans, while many crabs live in fresh water and on land, particularly in tropical regions. Crabs vary in size from the pea crab, a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 m.
Simplified: They look a lot like crabs and many have the word 'crab' in their name, but are not true crabs.