WordPress is a blog publishing system written in PHP and backed by a MySQL database. WordPress is the official successor of b2\cafelog and has a thriving user and developer community.

Distributed under the GNU General Public License, WordPress is free software. The latest release is version 2.1, released on January 22, 2007.

Beginnings of WordPress

The name WordPress was suggested by Christine Selleck, a friend of lead developer Matt Mullenweg.

WordPress currently supports one weblog or site per installation, but there is a multi-user version available called WordPress MU. Even with normal WordPress, a user can still have more than one WordPress blog in the same server, even on the same database, by placing the files in different subdirectories.

WordPress releases are named after well known jazz musicians (e.g. Mingus).

Source : Wikipedia