APM stands for Advanced Power Management. APM defines four power usage operating levels:
- Full On
- APM Enabled
- APM Standby
- APM Suspend
These power operating levels are now a subset of ACPI.
ACPI stands for Advanced Configuration and Power Interface. ACPI includes the power usage levels of APM plus two more. ACPI support a soft power feature. ACPI sets how to configure power management features in the BIOS settings and has seven power usage levels, called power states.