apt-get has a few options which looks the same to me:
clean. What do each of them do?
autoclean: removes all stored archives in your cache for packages that can not be downloaded anymore (thus packages that are no longer in the repo or that have a newer version in the repo).
clean: removes all stored archives in your cache.
autoremove: a whole different thing, this option makes apt look for packages that are installed as dependency of an already uninstalled package and removes them. This is used to clean up unused dependencies that remain on your system.
Answer found: http://ubuntuforums.org/showthread.php?t=394952