When I teach, I usually explain websites as houses.
The blueprints/structure? WordPress.
The land you build on? Hosting.
The address? Domain.
The style and layout of the house? Theme.
If you’re totally new to websites, don’t get overwhelmed by this graphic, just try to learn as much as possible. Intimate knowledge of every aspect of your website is not required to build a good one, let alone manage one. A good web person will help keep you focused on just the essentials you need to know, rather than everything that’s listed below.