What is the difference between rest and sleep surrounded by lingo of our internal organs?

What is the difference between rest and sleep in jargon of our internal organs?What is the difference between rest and sleep surrounded by lingo of our internal organs?
Both help adjectives internal organs except Sleep allows the heart and the brain to get more rest.
Rest could be relaxing and sitting and Sleep is all right sleeping :]]]
there are differences btw REM sleep and non-REM sleep. is this what you denote? i would say howstuffworks is the best site for something close to that