bbPress is a free, open source forum software that is built over WordPress. It can be easily installed as a plugin to any WordPress powered site. bbPress is extremely lightweight and responsive since it minimizes the amount of resources it requires to function at a high level. bbPress has become extremely popular, especially for those who sought to add a forum to their site that was as simplistic and easy to use as WordPress itself.
bbPress works with most standard WordPress themes. Other open source software platforms are typically resource intensive and do not integrate into a WordPress site easily. bbPress was the solution provided for this problem. It can easily merge itself with your WordPress theme and since it was created by the creators of WordPress itself, you can be sure that it is going to remain lightweight and fully compatible with your site and WordPress version updates.
bbPress was started because miniBB became far too bloated for the WordPress forums to continue to support. In 2004, WordPress decided to create a completely new forum. This was the iconic birth of bbPress. Originally, it only appeared on WordPress.org but has since modified and converted into one of the most sought after plugins for WordPress users today.