equery — View information about Portage packages. More information: <https://wiki.gentoo.org/wiki/Equery>.

List all installed packages

equery list '*'

Search for installed packages in the Portage tree and in overlays

equery list -po {{package1 package2 ...}}

List all packages that depend on a given package

equery depends {{package}}

List all packages that a given package depends on

equery depgraph {{package}}

List all files installed by a package

equery files --tree {{package}}