How people have dreams?
Do you mean how do people have dreams?
Apparently an average human has around 7 dreams an night, they
just can't remember them all.
All people dream, although some individuals do not remember
their dreams. Dreams are produced by the subconscious mind that
sorts through the thoughts, experiences and emotions of the day as
the conscious (waking) mind rests in sleep. Most dreams reflect
this sorting process, consisting of random images loosely strung
together into vague stories. Other dreams illustrate the dreamer's
deep emotions, particularly fear and anger, while other dreams
appear to be wish-fulfillment fantasies.