Just adding more on EFI..
Like TomTom mentioned you either have BIOS or EFI (Extensible Firmware Interface) also called UEFI. When you use EFI based systems you use GPT partitions. GPT partitions can address a disk more than 2TB which MBR can not at the moment. This is one of the major reasons of using GPT partitions in EFI based systems.
So when you have BIOS based systems, MBR is used. MBR cannot address >2TB
when you have EFI based systems, GPT is used. it can address >2TB.
by systems I mean : server,laptop,desktop.
some systems have the option of using either EFI or BIOS, so you can just go to the what we called BIOS settings in legacy term and change the system's behavior there.