A company called Automatic created and continues to develop the WordPress platform along with millions of independent developers who make plugins (features), themes, and add-ons for WordPress.  Most of all of these options are free.  Automatic allows you to create a free blog however in exchange for that you allow them to run advertising on your site.  If you would like to have your own site with no advertising then you have to host the website yourself through companies like us.  When you use an authorized third party hosting company you receive many additional features that Automatic does not offer like support, customization, and ad free websites.