- apt update – gets an up to date list of packages that can be installed or updated
- apt upgrade – updates packages it can, but never removes packages
- apt full-upgrade – updates packages more aggressively, removing packages that block other updates
- apt-get dist-upgrade an old name for
- do-release-upgrade upgrades to the latest operating system version
These are all confusingly named, and could have been called sync, safe-update, force-update, and upgrade-os.