The OS (operating system) is the software that runs all the other programs on a computer. Some examples of popular OSes are Microsoft Windows, Mac OS X, Android, and iOS. Here are some OS’s with a specific focus on privacy and security.
“Qubes OS is a security-oriented operating system. Qubes takes an approach called security by compartmentalization, which allows you to compartmentalize the various parts of your digital life into securely isolated compartments called qubes.”
“Tails is a live system that aims to preserve your privacy and anonymity. It helps you to use the Internet anonymously and circumvent censorship almost anywhere you go and on any computer but leaving no trace unless you ask it to explicitly.
It is a complete operating system designed to be used from a USB stick or a DVD independently of the computer’s original operating system. It is Free Software and based on Debian GNU/Linux.”
“Whonix is a desktop operating system designed for advanced security and privacy. Whonix mitigates the threat of common attack vectors while maintaining usability. Online anonymity is realized via fail-safe, automatic, and desktop-wide use of the Tor network. A heavily reconfigured Debian base is run inside multiple virtual machines, providing a substantial layer of protection from malware and IP address leaks. Commonly used applications are pre-installed and safely pre-configured for immediate use. The user is not jeopardized by installing additional applications or personalizing the desktop. Whonix is under active development and is the only operating system designed to be run inside a VM and paired with Tor.”