Help

$ sudo apt-get -h

Usage: apt-get [options] command
       apt-get [options] install|remove pkg1 [pkg2 ...]
       apt-get [options] source pkg1 [pkg2 ...]

apt-get is a command line interface for retrieval of packages
and information about them from authenticated sources and
for installation, upgrade and removal of packages together
with their dependencies.

Most used commands:
  update - Retrieve new lists of packages
  upgrade - Perform an upgrade
  install - Install new packages (pkg is libc6 not libc6.deb)
  reinstall - Reinstall packages (pkg is libc6 not libc6.deb)
  remove - Remove packages
  purge - Remove packages and config files
  autoremove - Remove automatically all unused packages
  dist-upgrade - Distribution upgrade, see apt-get(8)
  dselect-upgrade - Follow dselect selections
  build-dep - Configure build-dependencies for source packages
  satisfy - Satisfy dependency strings
  clean - Erase downloaded archive files
  autoclean - Erase old downloaded archive files
  check - Verify that there are no broken dependencies
  source - Download source archives
  download - Download the binary package into the current directory
  changelog - Download and display the changelog for the given package
...

Manage packages

Install package

$ sudo apt-get update
$ sudo apt-get install PACKAGE

Upgrade all

$ sudo apt-get update
$ sudo apt-get upgrade

Remove package

Uninstall package.

$ sudo apt-get remove PACKAGE

Uninstall and remove configs.

$ sudo apt-get purge PACKAGE

Remove all packages which were subdependencies before and are no longer needed.

$ sudo apt-get autoremove

Cache

Delete cached archive files. You can also use --dry-run to see paths that would be deleted.

$ sudo apt-get clean

Only delete archive files which cannot be downloaded anymore.

$ sudo apt-get autoclean