Plants need water to survive, which is an idea you’re probably already pretty familiar with. But a cactus is known for being able to live with very, very little water!
Cactuses (sometimes also called "cacti") are a type of plant called a "succulent," and are best known for living in hot, dry places like the desert, where they do not get a lot of water. Cactuses do need some water to survive, but can get along with a lot less than most plants.
One reason cactuses can get along with less water is because they don’t have leaves, so the water a cactus drinks does not evaporate as much as the water other plants drink. Additionally, cactuses have thick stalks which allow them to store water for a long time and roots that are good at finding and soaking up water even when its scarce! - Neat!