The dodo only lived on one island - Mauritius. When sailors arrived in the sixteenth century they found that the dodo was very easy to catch, and even though it didn't taste very nice, many were eaten.
The dodo's natural habitat was almost completely destroyed after people started settling on Mauritius. And when pigs, cats and monkeys were introduced, they added to the problem by eating the dodo and its eggs.
The last confirmed sighting of a dodo was in 1681 and by the end of the 17th century there were no dodos left.