Install/Disk Formats
In earlier times, there was only one way to boot a PC-compatible computer. All of our desktops and servers had standard firmware called the "PC BIOS," all our hard drives used Master Boot Records at the beginning of the disk, where the PC BIOS would "look" to find boot loader code which would in turn load Linux, and our hard drives were partitioned into different regions using the standard MBR partition scheme. That was just how it was done. And we liked it that way!
Then, along came EFI and UEFI, which are new-style firmware designed to boot systems, along with GPT partition tables to define disk partitions on disks larger than 2.2TB. All of the sudden, we had a variety of options for installing and booting Linux systems, turning what once was a one-method-fits-all approach into something a lot more complex.
Let's take a moment to review the options available to you for configuring a hard drive to boot Funtoo Linux. This Install Guide uses, and recommends, the old-school method of BIOS booting and using an MBR. It works and (except for rare cases) is universally supported. There's nothing wrong with it. If your system disk is 2TB or smaller in size, it won't prevent you from using all of your disk's capacity, either.
But, there are some situations where the old-school method isn't optimal. If you have a system disk >2TB in size, then MBR partitions won't allow you to access all your storage. So that's one reason. Another reason is that there are some so-called "PC" systems out there that don't support BIOS booting anymore, and force you to use UEFI to boot. So, out of compassion for people who fall into this predicament, this Install Guide documents UEFI booting too.
Our recommendation is still to go old-school unless you have reason not to. The boot loader we will be using to load the Linux kernel in this guide is called GRUB, so we call this method the BIOS + GRUB (MBR) method. It's the traditional method of setting up a PC-compatible system to boot Linux.
If you need to use UEFI to boot, we recommend not using the MBR at all for booting, as some systems support this, but others don't. Instead, we recommend using UEFI to boot GRUB, which in turn will load Linux. We refer to this method as the UEFI + GRUB (GPT) method.
And yes, there are even more methods, some of which are documented on the Boot Methods page. We used to recommend a BIOS + GRUB (GPT) method but it is not consistently supported across a wide variety of hardware.