Testing confirms that packages labeled "dependency" are those which are installed only because they are dependencies of other packages you have installed.
The package manager actually won't let you uninstall a dependency (as doing so would break the package that requires it). Similarly, uninstalling an "installed" package which is also a dependency of something else will not delete it, but instead downgrades it to "dependency" status.
You can conversely upgrade a dependency to an "installed" package by manually installing it. That will tell the package manager that you want the package to stay installed regardless of whether you keep the package(s) which depend on it.
Packages which were explicitly installed by the user are identified as such by adding them to
When you uninstall a package, the package manager will inform you if there are any dependencies which are no longer required, and suggest using
package-autoremove to uninstall them as well.