GRUB is a portable, powerful bootloader. This version of GRUB is based on a
 cleaner design than its predecessors, and provides the following new features:
 .
  - Scripting in grub.cfg using BASH-like syntax.
  - Support for modern partition maps such as GPT.
  - Modular generation of grub.cfg via update-grub. Packages providing GRUB
    add-ons can plug in their own script rules and trigger updates by invoking
    update-grub.
 .
 This package contains GRUB modules that have been built for use with the
 Xen hypervisor (i.e. PV-GRUB). It can be installed in parallel with other
 flavours, but will not automatically install GRUB as the active boot loader
 nor automatically update grub.cfg on upgrade unless grub-xen is also
 installed.