Dreams happen when people sleep.

Dreams are what a person sees and hears in their mind when they are sleeping. They are often similar to real life in some ways, but can also be very strange. Dreams can be so real, the person dreaming may not believe they are awake. This tends to happen during a false awakening, where a person dreams of waking up. A person has around 4 - 6 dreams per night, and tend to only remember the last two.