Similar to setting up a computer to dual boot two OS's, a multi boot system is designed to boot more than two different operating systems. This is getting more difficult to do because of security measures designed to prevent corruption of the boot sector of hard drives.
I used to have several desktops that could multi boot Windows XP, Windows 7, Red Hat Linux, and CentOS. I would switch them according to the project I was working on. I had to use the Linux boot manager because Windows does not play well with others.
I installed Red Hat first, setting up the master boot record using GRUB. Then I installed the Windows boxes, followed by the CentOS. It worked so well I cloned the box and used it for VMWare virtual machines. After the boxes were configured individually I had a whole server farm to work on projects. I also used this technique when working for Raytheon and Cabela's.
Iron Noder 2017