Flatpak
also: Flatpak application, Flatpak package
Flatpak is a containerized application packaging format for Linux that bundles an app with its dependencies, allowing it to run consistently across different Linux distributions without requiring system-wide installations.
Flatpak is a sandboxed application format that isolates software from the underlying system, similar to how a container works. Instead of installing packages through your distribution's package manager (apt, dnf, etc.), Flatpak packages include the application binary, libraries, and runtime environment needed to execute the app—eliminating "works on my system" problems.
Each Flatpak runs in a restricted sandbox with limited access to the filesystem, network, and system resources by default. Users can grant additional permissions explicitly, such as access to the home directory or audio devices. This improves security by preventing malicious or buggy applications from affecting the entire system.
Example: Installing the GIMP image editor via Flatpak would be flatpak install flathub org.gimp.GIMP, and it runs the same way on Fedora, Ubuntu, Debian, and Arch Linux without requiring different package formats.