Forums can have a description and you can use it as a presentation offering, maybe, links to other resources, to rules and so on.
To have that description displayed in the forum main page, you can code a custom theme part or use an hook. See the latter option.
bbPress has the action bbp_template_before_single_forum fired before every single forum page (ok, the name is pretty clear). Hence we need only to attach to it and print out the forum description.
add_action('bbp_template_before_single_forum', function () {
echo wpautop(bbp_get_forum_content());
});
The wpautop() makes the look a little better if you have not added HTML formatting tags in your description (the forum description has not a visual editor in the admin side, but you can use all the HTML you know).
Usually I like to add a featured image to my forums (and even to trend topics) so if they’re shared they look better on social networks.
Maybe you want to use the featured image in addition to the description to have a forum very nice presenting forum page. An example could be:
add_action('bbp_template_before_single_forum', function () {
the_post_thumbnail('large');
echo wpautop(bbp_get_forum_content());
});
(you may need to add some formatting HTML and probably a bit of CSS)
If your forum edit panel does not show the featured image, probably it isn’t, add even those two lines:
add_post_type_support('forum', array('thumbnail'));
add_post_type_support('topic', array('thumbnail'));