This Ubuntu icon is made in Material Design style developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 5,500 icons, all in the same style and quality.
The icon is comprised of a symbol basically identical to that used by the Ubuntu Linux distribution, enclosed within a circle. Ubuntu is one of the most popular Linux distributions, favoring a Mac OS X-like graphical interface, and with widespread support for most tasks one would imagine possible with a desktop computer.