The Grub system is pretty common on Linux desktops. Grub stands for GRand Unified Bootloader, and Grub2 is a continuation of its development. For a long time, another bootloader was also used by many distributions, called LiLo, which was short for Linux Loader, and while it is still actively developed, most distributions opt for Grub anymore.
Grub2 allows the user a degree of control before full boot, selecting which operating system to use, which kernel to use, and even allows for some security there, placing a password for pre-access. On highly sensitive systems, this can be useful. Grub2 also has a number of recovery options available via a somewhat limited shell that can [...]