An operating system is the most important software that runs on a computer. It manages the computer's memory and processes, as well as all of its software and hardware.
It also allows you to communicate with the computer without knowing how to speak the computer's language. Without an operating system, a computer is basically useless.
Modern operating systems use a graphical user interface, or GUI (pronounced gooey). A GUI lets you use your mouse to click icons, buttons, and menus, and everything is clearly displayed on the screen using a combination of graphics and text. Each operating system's GUI has a different look and feel, so if you switch to a different operating system it may seem unfamiliar at first. The three most common operating systems for personal computers are Microsoft Windows, macOS, and Linux. But not only computers have operating systems, other devices like smartphones have them too. The most common smartphone operating systems are Android and iOs.