Ubuntu is a Debian-based Linux operating system, with Unity as its default desktop environment (formerly GNOME). It is based on free software and named after the Southern African philosophy of ubuntu (literally, “human-ness”), which often is translated as “humanity towards others” or “the belief in a universal bond of sharing that connects all humanity”.
According to some metrics, Ubuntu is the most popular desktop Linux distribution. See Installed base section.
Development of Ubuntu is led by Canonical Ltd., a company based in the Isle of Man and owned by South African entrepreneur Mark Shuttleworth. Canonical generates revenue through the sale of technical support and other services related to Ubuntu.The Ubuntu project is publicly committed to the principles of open source development; people are encouraged to use free software, study how it works, improve upon it, and distribute it.
Ubuntu is composed of many software packages, the majority of which are free software. Free software gives users the freedom to study, adapt/modify, and distribute it. Ubuntu can also run proprietary software. Ubuntu Desktop is built around Unity, a graphical desktop environment.
Ubuntu comes installed with a wide range of software that includes LibreOffice, Firefox, Empathy, Transmission, and several lightweight games (such as Sudoku and chess). Additional software that is not installed by default (including software that used to be in the default installation such as Evolution, GIMP, Pidgin, and Synaptic) can be downloaded and installed using the Ubuntu Software Center or other APT-based package management tools. Programs in the Software Center are mostly free, but there are also priced products, including applications and magazines. Ubuntu can also run many programs designed for Microsoft Windows (such as Microsoft Office), through Wine or using a Virtual Machine (such as VirtualBox or VMware Workstation).
The Ubiquity installer allows Ubuntu to be installed to the hard disk from within the Live CD environment.
GNOME (the former default desktop) supports more than 46 languages.
For increased security, the sudo tool is used to assign temporary privileges for performing administrative tasks, allowing the root account to remain locked, and preventing inexperienced users from inadvertently making catastrophic system changes or opening security holes.PolicyKit is also being widely implemented into the desktop to further harden the system through the principle of least privilege.
Ubuntu can close its own network ports using its own firewall software. End-users can install Gufw (GUI for Uncomplicated Firewall) and keep it enabled.
Ubuntu compiles its packages using GCC features such as PIE and Buffer overflow protection to harden its software. These extra features greatly increase security at the performance expense of 1% in 32 bit and 0.01% in 64 bit.
Beginning with Ubuntu 5.04, UTF-8 became the default character encoding,which allows for support of a variety of non-Roman scripts.
sources from ->http://en.wikipedia.org/wiki/Ubuntu_%28operating_system%29