WordPress is a content Management system that was created by an American man named Matt Mullenweg and a British man named Mike Litte. Both men being bloggers developed wordpress in 2003. WordPress is made to post blogs but also can be used to create and design websites and is an open source product that allows users to modify as they wish.
WordPress.org is an open source and self hosted version of the wordpress platform that allows you to install the software on your own server, either on your computer or from web server. Self hosting offers more flexibility for creating and designing your site. All under your control being the domain name, web hosting and security.
WordPress.com is hosted on dedicated servers for company's that wish to make profit and choses WordPress as their base software. You are able to run your site while others look after your servers so you don't to. You also are granted fewer customization options along with obligated ads on your site, overall having much less control over your themes and plugins.
Overall, their are a lot of things that go into learning Wordpress and what options are suitable to you and your desired website. The beauty of WordPress is that it is suitable for anyone interested in creating their own site without the complexity of having to code everything. Although myself, I enjoy the web coding processes and eager to learn more on how wordpress is integrated with a code editor such as Visual Studio.