Of course, all commands to the service can also be submitted in the traditional way, via email. This is the most popular use of ListService. Only the moderator is permitted to send mail into the list. Moderator controlled lists are very useful for paid subscriptions, advertisments, or other 'broadcast' type information systems. The Community is a kind of email based chat group.
Any member can send mail into the list which is then distributed to all other members.
Either list type can be set up so that anyone can join or leave the list, or that the moderator controls list membership.