Flatpak is a package format for desktop GUI applications that runs each app in a sandbox, isolated from the host system and other apps. Unlike DNF/RPM (which installs system-wide and shares libraries), Flatpak bundles each app with its own runtime, so you can have GIMP 2.10 and GIMP 2.99 running side-by-side without conflict. It's mostly for workstations — servers don't usually care. On the RHCSA you'll see one or two basic questions: how to add the Flathub remote and how to install an app from it.
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