Ubuntu is a free and open-source Debian-based operating system that is created, developed and maintained by Canonical Ltd. Its name comes from the South African philosophy of ubuntu, which loosely means kindness or humanity towards others.
Its releases are time-based (that is, regular releases are made that follow a specific pre-defined time frame) with two per year: one in April and one in October. Each release of Ubuntu has its own unique version number, which is a decimal composed of two parts: the year minus 2000 (e.g., 15 for 2015) dot the month number (e.g. 04 for April and 10 for October). For example, the first release was in October 2004 and was 4.10, while in April 2015 the latest release was 15.04. Releases also have code names, which are composed of two words, the first is an adjective (e.g., Warty for 4.10, the first release) and the second is the name of a creature (e.g., Warthog for the first release).
In April of even-numbered years a Long-Term Support (LTS) version of Ubuntu is released. Hence, these releases have the generalized version number form: where . For example, 12.04 and 14.04 are the latest LTS releases.