Flatpaks are a new way of deploying applications. If you have an application already packaged as a Fedora package, creating Flatpak offers a number of advantages:
The application can be safely updated without rebooting the system (you can update a package without rebooting your system using dnf from the command line, of course, but GNOME Software only offers updating applications as part of an offline system update.)
The application can seamlessly be installed on Fedora Silverblue
The Flatpak works across all supported Fedora versions - you don’t have to update trailing versions of Fedora for people to use the newest application version.
The Flatpak can be run by people running on other distributions