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WordPress started in 2003 with a single bit of code to enhance the typography of everyday writing and with fewer users than you can count on your fingers and toes. Since then it has grown to be the largest self-hosted blogging tool in the world, used on millions of sites and seen by tens of millions of people every day.
WordPress is an Open Source project, which means there are hundreds of people all over the world working on it to make it better. It also means you are free to use it for anything from your cat’s home page to a Fortune 500 web site without paying anyone a license fee and a number of other important freedoms.
What You Can Use WordPress For
WordPress started as just a blogging system, but has evolved to be used as a full content management system and so much more through the thousands of plugins, widgets, and themes, WordPress is limited only by your imagination. (And tech chops.)
A Little History
WordPress was born out of a desire for an elegant, well-architectured personal publishing system built on PHP and MySQL and licensed under the GPLv2 (or later). It is the official successor of b2/cafelog. WordPress is fresh software, but its roots and development go back to 2001. It is a mature and stable product. We hope by focusing on user experience and web standards we can create a tool different from anything else out there.
For a bit more about WordPress's history check out the official WordPress page on Wikipedia.