REM sleep (rapid eye movement)
REM sleep is the final sleep phase. During this sleep phase, dreams are often experienced.
In the deep sleep phase the eye movement and muscle movements stop. The heart rate and breathing rate will slow down. It is difficult to be woken up during this phase.
Light sleep is the first phase. Eye movements and muscle activity become calmer and your body prepares for the deep sleep phase.
Waking phases should generally not occur during a good night's sleep but cannot be avoided.