What is EFI?
EFI is an Intel idea that will supposedly eventually replace the BIOS as we know it. EFI stands for Extensible Firmware Interface. You can read more about it at Intels site here.The main idea is that the BIOS has been around for so long its just not useful to todays computers. It slows them down. For instance a standard BIOS can only address 128K of option rom space. Most devices have option roms. So if you have an Adaptec scsi, a ATI video card and an Intel NIC. The BIOS loads these devices into memory. But lets say that the Adaptec device takes up 76K of option rom, the Intel NIC takes up 48K then there isnt enough for the video card or USB or any other devices etc(128K limit).
Common tricks to get around this limitation are to change the PCI scan order or disable some devices in the BIOS. The bottom line is the whole boot process and interaction between BIOS and the OS will be smoother, more efficient and faster.
AMI has a version of EFI called Aptio. Read about it here.