WordPress has two main web sites.
The second, WordPress.org, showcases what you can do with WordPress, especially when hosted on on your own, or a third party, web server.
This site is mainly for technical types, providing documentation on how WordPress works and the thousands of plugins that can be used to customize a web site. While there are fees associated with some third-party WordPress add-ons and themes, everything found on WordPress.org is available free of charge.
Most people using WordPress will never have to delve this deep to create useful and compelling web sites.