What is LINUX?
Technically speaking, Linux is the Kernel; the program in the system that allocates the machine's resources to the other programs that you run. Linux is normally used in combination with the GNU operating systems: the whole system is basically GNU with Linux added, or GNU/Linux.
Its under developement since 1991, started by Linus Torvalds.
Why use Linux?
- Most distributions are free
- Open-source (Completely customizable)
- Portable to nearly any hardware platform
- Highly scalable to lots of cores, or lots of memory
- Highly efficient, therefore useful for computaion
- Robust and proven security model
- includes a complete development environment
More info at Linux.com