Arid means really, really dry. When a place is arid, it doesn't get much rain or water, and everything there is very thirsty. Imagine if you were playing outside and you got really thirsty, but there was no water around for you to drink. That's what it's like for the plants and animals that live in an arid place. It's very hard for them to survive because they need water to live. Some parts of the world are arid because they are too far away from oceans or lakes, or because they are too hot and the water evaporates quickly. It's important to conserve and protect the water we have in arid places so that plants and animals can continue to survive.