Putting a device into a low-power mode where only RAM is powered to conserve power at the expense of time to resume operation
Sleep is a mode where only the RAM is powered. Related topics include the waking, power-management and hibernation where the contents of RAM are saved to storage and power is suspended from RAM as well. Apple combines sleep with hibernation under the marketing term "safe-sleep" where Macs will prepare for hibernation and then optionally enter it after a period of sleep to further preserve battery life.
