Obviously, everyone needs sleep. However, most people seldom think about how and why they sleep. We know that if we sleep well, we will feel rested. If we don't get enough sleep, we often feel tired and irritable.
Sleep seems to have two purposes: physical rest and emotional and psychological rest. We need to rest our body and mind. Both are important for our health. Every night we alternate between two kinds of sleep: active sleep and passive sleep. Passive sleep gives our bodies the rest they need, and prepares for active sleep, in which we dream.
Throughout the night, people alternate between passive sleep and active sleep. The brain rests, then becomes active, then dreams. Cyclic repetition: the brain rests, then it becomes active, and then dreams happen. This cycle is repeated several times throughout the night. During an eight-hour sleep, people dream for an average of one and a half hours.