An Acronym for Advanced Configuration and Power Interface.
The newer interface for changing devices' power status (eg on standby, hibernating, etc); supersedes APM.
Some example uses:
- spinning down idle hard drives,
- telling a monitor to go into lower power mode (but different from DPMS for going into standby)
- making a machine go into standby or complete hibernation
Many newer laptops use ACPI exclusively without support for APM. Linux kernel 2.4.x had some support for ACPI, but kernel 2.6 should have much better support.