Linux is a free and open source operating system which is similar to UNIX. Linux is developed as open source software means that the source code for an application is freely distributed along with the application. Linux's functionality, adaptability and robustness, has made it the main alternative for proprietary UNIX and Microsoft operating systems.
Many IT companies are working in Linux environment and others are thinking to move to it from windows as it is highly secured. Linux is popular because of its stability and security.