Sleep is important for your brain. Lack of sleep can change your mood, increase your anxiety, and decrease your immune system’s ability to fight infections. There are two sleep states. One is when you dream and the brain is as active as when you are awake. The other is when you have lower brain activity. This is when you rest and your short-term memories become long-term memories.
Fun fact: Brain activity can be recorded by electro encephalogram (EEG). This is an EEG recording of a brain during sleep.