Ubuntu is a computer operating system based on the Debian GNU/Linux distribution and distributed as free and open source software. It is named after the Southern African philosophy of Ubuntu ("humanity towards others").

Ubuntu is designed primarily for use on personal computers, although a server edition also exists. Ubuntu holds an estimated global usage of more than 12 million desktop users, making it the most popular desktop Linux distribution with about 50% of Linux desktop marketshare. It is fourth most popular on web servers, and its popularity is increasing rapidly.

Source: Wikipedia