I searched about it a lot and got something but. Can someone please explain in more simpler terms and why it is only used for fedora.And not for any other
According to their homepage :
RPM Fusion provides software that the Fedora Project or Red Hat doesn't want to ship. That software is provided as precompiled RPMs for all current Fedora versions and Red Hat Enterprise Linux 5 and 6; you can use the RPM Fusion repositories with tools like yum and PackageKit.
According to their FAQ :
RPM Fusion is a repository of add-on packages for Fedora and EL+EPEL maintained by a group of volunteers. RPM Fusion is not a standalone repository, but an extension of Fedora. RPM Fusion distributes packages that have been deemed unacceptable to Fedora.
The main reason of their existence is given here :
Fedora is effectively bound by the same legal restrictions as Red Hat, as a US company, is bound by. This means in particular that software encumbered with US patents cannot be included in Fedora.
In other words, it's a third party package repository for Fedora and RHEL distributions aimed at distributing software which cannot be included in the official repository due to legal considerations.