Multi-booting

rEFInd Boot Manager, with entries for openSUSE Tumbleweed (one is GRUB and another is kernel EFI stub) and Windows 11, an example of multi-booting
GRUB, with entries for Ubuntu and Windows Vista, another example of multi-booting

Multi-booting is the act of installing multiple operating systems on a single computer, and being able to choose which one to boot. The term dual-booting refers to the common configuration of specifically two operating systems. Multi-booting may require a custom boot loader.