Understanding GRUB2
The original GRUB, which is now referred to as GRUB Legacy, first came on the scene in 1995 as a replacement for the old LILO bootloader. It was easy to work with because it was easy to configure and it was implemented consistently on all Linux distros that used it. Unlike LILO, it can boot non-Linux operating systems. So, you can install Windows and Linux on the same computer, and GRUB lets you choose which one to boot up. GRUB Legacy worked well on the old BIOS-based computers, but it doesn't work with the newer EFI/UEFI computers. (Well, actually, the Fedora team did create a forked version of GRUB Legacy that would work with EFI/UEFI, but they abandoned it in favor of GRUB2 in 2013.)
GRUB2 isn't an update of GRUB Legacy. Instead, it's a whole new bootloader that was created from scratch. Now, I have to tell you that there are both good things and bad things about it. The good thing is that it can work with the new EFI/UEFI computers. The bad...