WordPress.com or just WordPress?

Hello

WordPress.com is a platform for bloggers who are given permission to create a blog that is hosted by WordPress.com themselves. There are themes you can buy via their internal mechanism.

If you want freedom to use and upload plugins and themes that you like you need to register a domain and also buy some hosting and install the WordPress in the server. That means you have to create a self hosted WordPress site to upload the theme and know that WordPress.com(blogging platform hosted by them) and WordPress.org(Self hosted CMS) are two different things.

for detail visit http://codex.wordpress.org/FAQ_About_WordPress#What.E2.80.99s_the_difference_between_WordPress.org_and_WordPress.com.3F