The digest version Subscribers receive multiple posts in a single mail message, at regular intervals, or when a lot of posts have accumulated. Subscribe by e-mailing <email@example.com>.
The no-mail version Subscribers do not receive any posts from the list. This means, though, they are able to post to a list which only subscribers may post to, while they follow the list using a web archive or another subscribed email address. Subscribe by e-mailing <firstname.lastname@example.org>.