Final answer:
The author likens sleeping to 'sleep' mode on a computer to illustrate that sleep has restorative and cognitive functions for our brains.
Step-by-step explanation:
The author compares sleeping to "putting a computer into 'sleep' mode" to help readers understand what our brains do when we sleep. This analogy is used to convey the concept that sleep serves important restorative and cognitive functions, much like when a computer is in sleep mode, it is not entirely off but rather in a state of reduced activity ready to resume full functionality upon waking. This comparison emphasizes the brain's need to reduce functions to consolidate memories, process information, and restore itself for proper functioning during wakefulness.