Noun
sleep mode (usually uncountable, plural sleep modes)
(computing) the state of a computer system in which the drives and interfaces are switched off, and the only task running is monitoring external activity, particularly a key press which restores the system to its active state from the random access memory.
Synonyms: standby, suspend to memory, suspend to RAM
Coordinate term: hibernation (“a mode that completely powers off and restores from hard disk”)