Apt-get is pretty much deprecated, because modern apt does everything it did and more. Once upon a time apt-get was useful, but that time has passed. The only things absolutely necessary are 'apt update', which refreshes the available new package database, and either 'apt upgrade' or 'apt full-upgrade', depending on what you're running. For Stable, full-upgrade is superfluous, but if you're running Sid or Testing, it will remove packages if needed. Never, ever use the -y option if you're running either Sid or Testing, because bad things will happen at some point. Blindly accepting everything apt proposes is a ticket to disaster, because you need to check to make sure essential packages aren't going to be removed. Because so many packages are sometimes in the pipeline, they may not be in the correct order every time you update, and dependency issues can blow everything up. It's relatively safe in Stable, but I still will never do it. Murphy was an optimist wearing rose-colored glasses. All the rest of the commands are optional. I tend to use the autoremove command just to keep things tidy, but having unnecessary packages only takes up a little bit of storage space, no other downsides. Autoclean removes downloaded .deb files, which only take up some storage space, and might be convenient in a few instances. It's fine, because the packages can always be downloaded again, but not strictly necessary unless you're very, very short on system storage. Using --purge is probably good practice most of the time, but not always. It removes user data and configs, which isn't always desired. Choose wisely.