A Video Introduction to BuddyPress Groups
BuddyPress is the social networking plugin for WordPress.
You can create public, private or hidden (invite-only) groups.
A BuddyPress group is very similar to a Facebook group and allows your members to organize themselves based on their interests.
This video is part of our complete “Introduction to BuddyPress” class.
How can users join groups without invitation?
The group has to be marked in its settings as either public (any site member of the site can join it) or private (any site member can request to be able to join). Hidden groups require that the admin of that group send invitations. Here is a link to the [url=https://buddypress.org/about/groups/]BuddyPress documentation on Groups[/url]. Hope this helps!