An open source operating system is an operating system whose source code is publicly accessible and editable. The term "open source" refers to software with source code that anyone can inspect, modify, and enhance. Open source software is different from proprietary software in that its authors make its source code available to others who would like to view, copy, learn from, alter, or share it. Closed operating systems, such as Microsofts Windows and Apples iOS and Mac OS, are built with numerous codes and complex programming that is kept secret by the respective companies and inaccessible to third parties.

Open source operating systems work similarly to closed operating systems, but the difference is that in open source operating systems, the source code or the whole application is modifiable by the user. There is no defined way or framework for how open source operating systems work, and they can be customized based on user needs.

Some examples of open source operating systems include Linux, FreeBSD, and OpenBSD. Open source operating systems are cost-efficient, reliable, and secure because developers are also users of the operating system and can resolve any bugs or issues in the source code.