Actually when we sleep we thing we r taking rest but, our body is actually repairing at top gare , it prepares the whole body for the next day ahead, and our mind ie. aka brain is firing up all its neurons to check & maintain the connectivity between neurons, as more the neurons are connected to each other the more is the brain active,but as u see are main activity during the day time is seeing things ,that takes up most of our brain resources ,so when we r asleep this activity is nil so most of our brain resources are freed & so back processes get active like storing of memory ,&etc.

so u see neither our brain & our mind takes rest (as the major activities are nil but body & mind are at full speed working at cell level ! ) its just us whos conscience mind is minimal active & because of that we think that we are resting , ;)

Mind essentially,body incidentally.

Hanjni true andmidn has luxury of dreaming dear