Succulent plants are plants that store water in their leaves or stems oder roots.
Actually every plant stores water but succulent plants are specially adapted to store water for a longer period. So they can exist at dry places and have not much concurrence there. The habitats are mostly very sunny. At day it is rather hot there, at the night it is mostly cool. Then the succulents can respirate. In the morning often dewfall helps the plants to survive.
There are succulent plants in many families (more or less 50), however for some families every member is succulent; for example the Cactaceae, Agavaceae and Crassulaceae.