GRUB (GRand Unified Bootloader)
GRUB (GRand Unified Bootloader) is a boot loader package developed to support multiple operating systems and allow the user to select among them during boot-up.
GRUB was created by Erich Stefan Boleyn and has been further developed under the GNU project as GNU GRUB. The original package, sometimes known as GRUB Legacy, is still available for download but no longer being developed.
GRUB's name is a reference to the Grand Unified Theory (GUT) of physics.