LTS
LTS is an abbreviation for “Long Term Support”.
We issue a new desktop and server release every six months. That means you'll always have the latest and greatest applications that the open source world has to offer. Ubuntu is designed with security in mind. You get free security updates for at least 18 months on the desktop and server.
A new LTS version is released every 2 years. With the Long Term Support (LTS) version you get 3 years support on the desktop, and 5 years on the server. There is no extra fee for the LTS version, we make our very best work available to everyone on the same free terms. Upgrades to new versions of Ubuntu are and always will be free of charge.
The two LTS releases so far are DapperDrake and HardyHeron. The next LTS release will be LucidLynx, released in April 2010.