We need sleep to survive. Sleep restores us. There is no magical number of the amount of sleep that can be used as a benchmark for everybody.
Every person has their own requisite amount of sleep that is required to function each day.
The REM sleep is related to dreaming and occupies about a quarter of our sleeping hours. REM sleep is characterized by a high level of activity. In fact, your heart rate, blood pressure and breathing are similar to what you experience when you are awake. In addition, it is believed that memories are consolidated during this stage of sleep. In contrast, heart rate and respiration slow down and blood pressure declines during the deepest stages non-REM sleep, believed to be the most physically restorative time for the body.