Tool use is when we use things other than our bodies to help us do things. Just like how you might use a pen to write or a fork to eat, animals use things like sticks or rocks to help them do things too!
For example, some birds use sticks to help them reach into holes to get food, and some primates use sticks to poke at insects and get a snack. Even some animals that you wouldn't expect, like octopuses, use tools! They have been known to use coconut shells or other objects to help them hide or even carry around some of their babies!
Using tools takes a lot of thought and problem solving because you have to figure out which tool will work best for what you want to do. Even though humans are very good at using tools, we aren't the only ones who can do it! Lots of animals are pretty smart and can figure it out too!