Correct. Now that I re-think about it, I guess it's kind of similar to whodunit.
At the start of the game, in the scenario that only a mafia group and town are present, mafia knows who the town is since, in the first pm you receive stating your role (the one you have received with your role in it), the mafia team receives their roles as a group so they already know who is in their team and what role they each have. Therefore, they also know who the town is since there is only one mafia group. However, the town doesn't know anything because we start as individuals (most of the time) and not as a group. The roles themselves are randomly giving by the hosts.
The PM function is used to communicate with the hosts. If your role has an action attached to it, you state your action and your target in a message to the hosts (almost always at night) so your action can go through. So let,s say you want to investigate Equaling Heaven, you message the hosts ''I would like to investigate Equaling Heaven tonight'' then the hosts will take a note of it and message you back at the end of the night stating the result you got. About the CIV mechanic, I believe you only have to tell the hosts whether you're going to explore the coastline or the mountains. I'd ask the hosts for more details.