It is pretty easy to get confused between “wordpress.org” and “wordpress.com”, especially when setting up a new site or choosing themes. This video offers an overview of what sets the two apart.
When you see “wordpress.org” or references to the “.org” version of WordPress. it is referring to the self-hosted, downloadable version of the WordPress web software. This version gives you the utmost control over your site, and is available from most hosting companies as a free add-on.
See Installing WordPress for further details
The “.com” version of WordPress is an affiliated commercial service offering hosted WordPress blogs for free or a premium monthly fee. WordPress.com accounts are restricted in several ways, including theme and plugin choice, installation and customization. While this is a more limited version of WordPress, it offers the benefit of a huge community of users, support, stability, security and a simplified administration experience, which is beneficial if you have a simple blog or are just starting out.