A BootLoader is the first software program that runs when a computer starts. It is loaded by the BIOS at the end of hardware initialization and is responsible for loading the OperatingSystem Kernel and transferring control to it.

A multiboot loader offers a menu and the ability to select from a list of operating systems. Multiboot loaders include:

• GRUB
• LILO
• SysLinux, IsoLinux, ExtLinux. These are three related bootloaders from the same author, and using pretty much the same config files. The difference is that SysLinux boots off FAT volumes, IsoLinux off ISO9660 volumes (e.g. CD-ROMs and DVDs), and ExtLinux off Ext2/Ext3 volumes.
• Windows' NT Bootloader, NTLDR
• Smart Boot Manager, which has lots of uncommon features.

You can chain BootLoaders, eg. GRUB can load up Windows' BootLoader (this is the preferred method for DualBooting Linux and MicrosoftWindows.)

There's also a strange beast called LoadLin.