After this unit and before buying a domain and/or hosting read the Unit Registering your Domain Name and Buying Hosting.
Your website will be made up from a bunch of files and these files need to be stored somewhere on a server that is connected to a fast Internet connection so that people can look at it via a web browser on their computer or mobile device. Website hosting is necessary for all websites.
WordPress is the software that will drive your website. For WordPress to operate, it needs to be installed on the server where you will be hosting your website.
The hosting you buy must be able to support WordPress as WordPress has certain requirements. Most hosting providers do support WordPress and offer a simple one-click installation method for installing WordPress (recommended), more about this in the next section.