It is administered by LISTSERV software, which means that most of the day to day operations are performed automatically - when you send a message to the list, it is automatically forwarded to all the subscribers. Subscription requests and other administrative messages are dealt with by computers, not humans, so they have to be submitted in a format that the software can understand. Some of the main admin messages are detailed below.
As it is a mailing list, not a newsgroup, everyone on the list has to receive everything anyone sends, so be a bit considerate when posting - subscribers may be on services like CompuServe which charge for every piece of mail received, and they won't have the option of refusing posts they might not be interested in. This isn't to say you should be afraid of raising subjects of marginal interest - we're all here to learn, and there are a lot of apparently esoteric aspects of multimedia that may become central in the blink of an eye - just that long dreary flamewars and similar Usenet traditions are best left on Usenet.