What Does Host Operating System Mean?
A host operating system is the primary operating system (OS) installed on a computer system's hard drive. In most cases, there is only one host OS. Other OSs, known as virtual OSs, may operate within the host OS.
Techopedia Explains Host Operating System
When virtual operating systems are required to deal with computer resources in different ways, one or more virtual operating systems are installed within the host operating system, allowing the operating systems to function simultaneously. However, the host operating system must boot first, then the other operating system(s) boots.