Don’t feel overwhelmed by all this info as there are details on how and where to register a domain name and set up a hosting account in the Resources section at the end of this course.
The difference between WordPress.com and WordPress.org is:
WordPress.com provides an extremely quick and easy way of getting up and running, it provides free hosting and automatic updates at the cost of having a limited set of themes and plugins to choose from and a very limited degree of customisation. You also need to pay for additional services such as having a bespoke domain name, increasing disk storage or removing advertising.
WordPress.org is where you download WordPress for installation on your own server and where you can find all the documentation for it. Self-hosting WordPress allows for complete control over every element of your website/blog with no restrictions on themes or plugins, and is the preferred route forward for a serious website/blog.
You can always start off with a WordPress.com account and move it to a self-hosted alternative when you’re ready, although there will be a small cost involved in doing this.