Linux is an operating system similar to Unix. The USP of Linux is primarily that it is open source software. This means that the underlying source code can be freely used and modified without restriction and cost. It can also be redistributed commercially and non-commercially as long as the stipulations are followed. It is predominant on servers and is recently being popularized and adopted onto desktops owing to the number of distributions in Ubuntu. Another reason that is driving Linux adoption is the emergence of Net-books and Laptops.
The gentleman who visualized and implemented the concept of Linux is Linus Torvalds who wrote the Linux Kernel in 1991. Other components of the system include the HTTP Apache Server, the X Window System, the GNOME and KDE desktop environments. Additionally, the system also encompasses utilities and libraries from the GNU project. Commercially, Linux is now used in embedded systems, mobiles, watches, servers, computers, notebooks and Net-books. Support is also growing for Linux owing to the fact that it is inexpensive, more robust and virus free. The mascot of the operating system is Tux, the Penguin.
Linux has now branched out and several vendors have customized and developed their own distributions taking into account the market and customer requirement. Some of these distributions are on volunteer basis like Debian while others maintain a community commercial licensing system like Red Hat and Fedora. Examples of different distributions of Linux are Debian, Fedora, Knoppix, Mandriva, OpenSUSE, Red Hat Enterprise Linux and Ubuntu. This is not an exhaustive list.