In a Nutshell, Linux is an Opensource Operating System which is entirely different to Windows OS and very much similar to Unix OS.
Microsoft Windows versions have been developed and are being sold by Microsoft Company.End users like us are expected to pay fee/money for using their services and GUI (Graphical User Interface) is at its peak in Windows Operating System. Also, many of the applications are being run and developed in Windows environment,so it obvious that most of end user machines will run on Microsoft OS.
Unlike Windows OS, Unix/Linux systems are used at admin/Server level, since these OS’s are proven to be a stable systems and easy to maintain by admin users.Also vulnerabilities to outside hack attacks are less in these kind of systems.
Beauty of Unix and Linux Systems are that ,these systems still work with command line arguments at server level (GUI is available in linux Flavors like Ubuntu,Mint,fedora for performing most of operations)