Complementary metal oxide semiconductor (CMOS) refers to a chip inside your computer that saves your BIOS settings. As a result, the terms CMOS & BIOS are sometimes used interchangeably.
Advanced Configuration and Power Interface (ACPI) is an industry standard that describes power management features and other configuration information for computers. Some last versions of BIOS do not support ACPI, and so the computer may not successfully enter advanced power modes like sleep or hibernate.