It's really quite simple; rvforum.net is the domain and I have that url set to go to the Home pags of our web site. This hasn't changed over the last 10 or 12 years, including when we were hosted on Compuserve and were using their forum software. The Home page of the web site has links to various parts of our site, including these message boards.
If you look in the top left of the page you're reading, it says 'The'RV Forum Community', partly to distinguish these message boards from other parts of our site (such as the forum Library and photo gallery). These words show up in search engine listings of content within our message boards and, yes, there will be many such listings. The url for any such content will be of the form rvforum.net/SMF_forum/... because our forum software (called SMF) resides in a directory of that name.
Similarly, our Library runs on software called joomla, which resides in a directory of the same name. So, urls for library content will be of the form rvforum.net/joomla/... and, again, there will be numerous such listings in search engines.
A similar story for our photo gallery, which runs on software called Coppermine Photo Gallery and which resides in a directory called 'coppermine'. urls for the various albums and photos are of the form rvforum.net/coppermine/...
All the above is subject to change if/when I replace any or all of the software with different platforms, and depending on what redirects I decide to set up.