All members can private message (PM) one another once they have passed visitor status posting,
but
I am not sure what you mean by "Maybe a moderator can forward your PM's to me or another member."

Only members have access to their own PMs!
Moderators do *not* have access to member PMs. That is why they are called private messages.
If a member wants to send a direct PM to a moderator they can do so, or they can forward a PM sent to them by another member if they want a moderator to review it, but no moderator is able to enter a member's PM box