Final answer:
Sleep is essential for restoring our body's energy and supporting brain functions such as memory and learning. Lack of sleep can lead to slower thinking, forgetfulness, and a weaker immune system.
Step-by-step explanation:
Scientists have suggested a couple of reasons why humans need sleep. One reason is that sleep helps restore what our bodies have used up during the day, kind of like how your toys need to recharge after you've played with them a lot. Another reason is that sleep is super important for our brains to work properly.
It helps us remember what we learn, like the steps to a dance or answers for a test. When we don't get enough sleep, we might feel slow, forget things, or even get sick more easily.