The operating system you choose/use provides your computing environment. While most people only know about Microsoft Windows, or Apple's OSX, there are a great number of alternative operating systems which are not only better in terms of the stability, features and performance; they are also freely licensed. The most popular freely licensed system in the world today is the Android operating system used by Google on it's mobile devices. For desktop and server platforms, it's Canonical's Ubuntu.
There are continually new options. The 'NixOS' offers a linux-based system that is more for the development operations crowd. https://nixos.org/nixos/about.html