Do our Brain flushes out toxins only when we sleep?Is that the reason for sleep?

Dear Student,
Yes, various studies have proven that our brain flushes out toxins when we sleep. But, we sleep basically due to the following reasons:
Sleep is a behavioural state that is natural part of every person.  When we sleep our body get relaxed. When we move into different stages of sleep, then various changes occur. In stage of onset of sleep we become disengaged from surroundings and become partially unconscious. Our brain works for various things other than awareness about surroundings during sleep. Brain works for various maintenance processes throughout the sleep. Slowly our muscles become relaxed, breathing rate slows down, blood supply to muscles increases, and the brain induces the cells to grow very fast and repair and heal the wounds. We start dreaming in the stage of strong sleep.
Regards