clean
clean clears out the local repository of retrieved package files.
It removes everything but the lock file from
/var/cache/apt/archives/ and /var/cache/apt/archives/partial/.
autoclean (and the auto-clean alias since 1.1)
Like clean, autoclean clears out the local repository of retrieved
package files. The difference is that it only removes package files
that can no longer be downloaded, and are largely useless. This