Sleep is natural and resting state of which involves altered state of consciousness which is characterized by reduced sensory activity and retardation of voluntary muscles while trance is heightened state of awareness where the person is disassociated from the external environment. During trance the suggestibility is high and the individual is more focused. In trance the conscious is altered but not absent, the individual does respond to the external stimuli depending the depth of trance.
The key differences between sleep and trance are:
Trance is induced intentionally for the purpose of therapy or relaxation while sleep is a physical natural state essential for our health.
During trance your conscious is altered but still active, but when we’re sleeping there is significant reduction in our consciousness and awareness.
While we’re in trance we can respond to certain external stimuli, but during sleep we don‎’t responds to stimuli unless they are strong enough to awake us.
Trance activates theta waves of brain that is associated with relaxation and focused attention while during REM stage of sleep the brain has high activity due to distinct patterns.