One of the most important factors in SEO is robots.txt. If you have the wrong entries it could end up telling search engines not to index your site, which means it will not appear in search results.
The first thing that BF SEO does is check to see if you have a robots.txt file in your website root. If not, you have the option of creating one. A Joomla site normally comes with a robots.txt.dist file, so the software will attempt to create your robots.txt file based on that. If your site does not have a robots.txt.dist file, then a basic robot.txt file will still be created.