An edition of Ubuntu which provides server applications and a text-mode environment in place of a GUI. You may want to consider asking on http://askubuntu.com/.
Ubuntu Server is an edition of the Debian-based Ubuntu Linux distribution designed for use on servers. The default installation eschews the X Window System and desktop environments in favor of a text-mode environment, and provides essential packages for use on servers such as Apache and MySQL. Ubuntu Server shares the same APT package repositories as the desktop edition, so the same packages can be installed on both editions.
You may want to consider asking Ubuntu-specific questions on one of our sister sites, Ask Ubuntu.