Google Groups are set up mainly as email distribution lists.  Some vary, depending on that Group's particular need.  One of the most popular questions is how a community member determines what groups to which they are subscribed. Here is how:

From The Google Workspace App Launcher, locate Groups.  Once the Groups App is open, you'll see the following on the right side of the app:

If you do not see a Group that you feel you should be a part of in the "My groups" section, you can make a request by placing a ticket on FreshDesk or contacting the appropriate Division Head/Assistant.