In my opinion, update is kind of a misnomer, as it only means “look for updates” in this context.
Other apt options
$ apt --help
This is the Linux Mint "apt" command.
This commands acts as a wrapper for the APT package manager and many other useful tools such as apt-get, apt-cache, apt-mark, dpkg, aptitude...etc.
It is installed in /usr/local/bin/apt. To use the upstream apt command directly type /usr/bin/apt.
Usage: apt command [options]
apt help command [options]
Commands:
add-repository - Add entries to apt sources.list
autoclean - Erase cache for packages no longer available
autopurge - Erase system-wide config files left by removed packages
autoremove - Remove dependency packages no longer required
build - Build binary or source packages from sources
build-dep - Configure build-dependencies for source packages
changelog - View a package's changelog
check - Verify there are no broken dependencies
clean - Erase downloaded archive files
contains - List packages containing a file
content - List files contained in and installed by a package(s)
deb - Install a local .deb package
depends - Show package dependency information
dist-upgrade - Fully upgrade the system by allowing other package changes
download - Download packages to the current working directory
edit-sources - Edit /etc/apt/sources.list with your preferred text editor
dselect-upgrade - Follow dselect selections
full-upgrade - Same as 'dist-upgrade'
held - List all held packages
help - Show help for a command
hold - Hold a package
install - Install and/or upgrade packages
list - List packages handled by the system (e.g., installed)
policy - Show policy settings
purge - Remove packages and their system-wide configuration files
recommends - List missing recommended packages for a particular package
rdepends - Show reverse dependency information for a package
reinstall - Reinstall packages or install if not yet installed
remove - Remove packages
search - Search for a package by name and/or expression
show - Display detailed information about a package
showhold - Same as 'held'
showsrc - Display source package records matching the given package
source - Download source archives
sources - Same as 'edit-sources'
unhold - Unhold a package
update - Download lists of new/upgradable packages
upgrade - Perform a safe upgrade
version - Show the installed version of a package
I think that it means “uptdate the local list/database of packages”.
For example, you might do:
apt install somepackage
without doing
apt update
first. That might or might not do what you want, since “somepackage” might have been updated since you last updated your local package list. the install would try to download the old version, which would not be found.
What you think of as update debian calls upgrade. I welcome this granularity.