Ubuntu is a Debian-based Linux operating system and distribution, with Unity as its default desktop environment. Development of Ubuntu is led by UK-based Canonical Ltd., a company owned by South African entrepreneur Mark Shuttleworth. Canonical generates revenue through the sale of technical support and other services related to Ubuntu.
A default installation of Ubuntu contains a wide range of software that includes LibreOffice, Firefox, Thunderbird, Transmission, and several lightweight games such as Sudoku and chess.
Ubuntu 14.04.3 LTS (long-term support) is the latest version of the OS. I have only run it from a thumb-drive, even so I found it to be quite snappy performance wise which was a surprise after my last foray into Ubuntu a couple of years ago. I found it quite sluggish but it looks like it has improved tremendously.