System software refers to a system that controls and coordinates computers and external devices, supports the development and operation of application software, and is a collection of various programs without user intervention. Its main function is to schedule, monitor and maintain computer systems. Responsible for the management of various independent hardware in the computer system, so that they can coordinate their work. System software enables computer users and other software to regard the computer as a whole, regardless of how each underlying hardware works.
Having said that, if you only know a little about computers, you are basically at a loss. You can understand it this way:
Operating system is the interface between human and physical machine (hardware). The application software must run on the operating system, because it must be given a bearing platform.