Related question: I assume forum posts don't get automatically sent to group members but that you have to actively go check the forum for posts. So that doesn't necessarily help me contact all group members. Right?
'Post News' and 'Message' What's the difference?

I got your message via my email box. That appears an effective way to communicate.
How are things going? Good to hear from you again!
I've a pretty basic question, I think. I'm not sure about the different ways to communicate to members of a group I've organized. I want to get information out to the entire group in a way that I can be sure each group member is most likely to see.
I'm confused about the difference between 'post news' and 'message' - and, for that matter, topics in a forum.
At times I've gotten an alert about some kind of activity, but haven't always been able to figure out what that activity was. So I'm wondering if others in my group could easily miss the information I'm trying to get to them.
Help!