Enter the server buffer (gnus-group-enter-server-mode). See The Server Buffer.

Post an article to a group (gnus-group-post-news). If given a prefix, the current group name will be used as the default.

Mail a message somewhere (gnus-group-mail).

is called after the group buffer has been created.

is called after the group buffer is generated. It may be used to modify the buffer in some strange, unnatural way.

is called as the very last thing after the group buffer has been generated. It may be used to move point around, for instance.

Groups matching this regexp will always be listed in the group buffer, whether they are empty or not.