Quoting from Wikipedia
Linux is a Unix-like and mostly POSIX-compliant computer operating system (OS) assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel an operating system kernel first released on 5 October 1991 by Linus Torvalds. The Free Software Foundation uses the name GNU/Linux to describe the operating system
- Speed, Security, Stability
- Highly configurable
- Multiuser environment by default
- Well defined hierarchy and permissions to allow networking across different groups and sites
- Strong set of commands to automate repetitive manual tasks
- Read more on using Linux and does it fit your computing needs on computefreely
- Servers
- Supercomputers
- To quote TOP500 article on wiki, "As of November 2015, 494 or 98.8% of the world's fastest supercomputers use the Linux kernel"
- Embedded Systems
- Smart phone and similar
- Android - built on top of Linux kernel
- iOS - Unix based
- Personal and Enterprise Computers
- And many more uses, thanks to being open source
- Usage Share of Operating Systems
Like how numerous programming languages exist, there are various Linux flavors called 'distribution' (distros for short), to cater the needs of beginners to advanced users as well as highly customized as per end use case
- There are hundreds of known distributions
- One can keep track of them at distrowatch
- Popular Linux Distros compared
- Light Weight Linux Distros
- Check out article comments also
Installation
Usually, you'll find installation instructions from respective website of the distro you chose. If you need an overview of installation process, this should help