From Gentoo Wiki
A bootloader is a program that loads bootable items when the system is started.
Depending on the architecture of the machine, several bootloaders are available:
|Using the (U)EFI firmware to directly load a Linux kernel, skipping the use of a secondary bootloader.
|Reworked version of GRUB. Gentoo's default bootloader on x86 and amd64.
|Simple boot loader with some advantages over GRUB and GRUB2.
|Boot manager for EFI and UEFI platforms.
|Collection of simple bootloaders for various purposes.
|Bootloader that is specific to UEFI firmware and the systemd init system.
|Bootloader popular with embedded devices. See also U-boot-tools.
- Security Handbook/Bootloader security — boot path security.
- Embedded Handbook/Bootloaders
- Comparison of boot loaders (Wikipedia)