Ubuntu is an operating system based on the Debian Linux distribution. It was built as a free alternative to Microsoft Windows and Mac OS. Ubuntu can run on many older computers that the other two OSs can not. The main page for Ubuntu is www.ubuntu.com. Here you can find documents for install not only Ubuntu but many other aspects of the operating system. On the homepage you can find Ubuntu desktop, cloud, business, and server editions. The operating system uses Libre Office instead of Microsoft office. Also the command line uses commands that all three operating systems use. It also uses different commands an example would be , ifconfig in Ubuntu as Windows uses ipconfig. Many of the process to run Ubuntu have been moved to the background or given one-click icons to launch the process. This has made it easier for beginners to use the system.  
Linux was developed in 1991 as open source software, this means that the source code can be manipulated by the public to either make alterations that improve it, or to customize it towards a specific application. This allows for a people all over the world to collaborate and change the software in ways they see beneficial to either the general public or a private business who is looking for an operating system that can do some more specific things than a normal operating system can. Many people choose Ubuntu as their go to operating system because it is completely free, and as far as software goes, it isn't missing anything that other operating systems have.