Note: Some older Intel Server boards are known to operate on Intel EFI 1. Only some older macs use i386 EFI firmware while no non-Apple UEFI system is known to use i386 EFI firmware. Most of the UEFI firmware in the market, including recent Apple Macs use x86_64 EFI firmware. Under UEFI, every program whether they are OS loaders or some utilities (like memory testing apps) or recovery tools outside the OS, should be a UEFI Application corresponding to the EFI firmware architecture.
An EFI System Partition is usually formatted as FAT32. Each vendor can store its files under /EFI// folder and can use the firmware or its shell (UEFI shell) to launch the boot program.
Instead it uses a special partition in the partition table called «EFI SYSTEM PARTITION» in which files required to be launched by the firmware are stored.
UEFI does not launch any boot code in the MBR whether it exists or not. EFI in Apple-Intel Macs can access HFS/HFS+ filesystems also apart from the mentioned ones. Most of the UEFI firmwares have support for accessing FAT12 (floppy disks), FAT16 and FAT32 filesystems in HDD and ISO9660 (and UDF) in CD/DVDs. EFI in Apple-Intel Macs are known to support Apple Partition Map also apart from MBR and GPT. The commonly used UEFI firmwares support both MBR and GPT partition table. UEFI has support for reading both the partition table as well as understanding filesystems. UEFI firmware does not support booting through the above mentioned method which is the only way supported by BIOS.