The list server relays messages from members of the forum to all of the participants. Responses are directed back to the forum so everyone can read the discussion. Since forums like this can generate many messages there are two ways to subscribe. In "Individual" mode each message will be sent to you as soon as it is received by the list server. In "Digest" mode a days worth of messages will be collected and sent as a single message. The list server will send multiple digests in a single day if necessary to keep the size of the digests reasonable.
To subscribe, send an email to firstname.lastname@example.org from the account you wish to receive emial to.