Find bogus groups and delete them (gnus-group-check-bogus-groups).

Find new groups and process them (gnus-group-find-new-groups). With 1 C-u, use the ask-server method to query the server for new groups. With 2 C-u's, use most complete method possible to query the server for new groups, and subscribe the new groups as zombies.

Run all expirable articles in the current group through the expiry process (if any) (gnus-group-expire-articles).

Run all articles in all groups through the expiry process (gnus-group-expire-all-groups).