From Fedora Project Wiki

There are a number of third-party software repositories for Fedora. They typically have more liberal licensing policies and provide software packages that Fedora excludes for various reasons. These software repositories are not officially affiliated or endorsed by the Fedora Project. Use them at your own discretion. A detailed list is maintained at Ask Fedora page

The RPM Fusion repositories are commonly used by end users. RPM Fusion's packages are layered in several repositories.

There are a number of other repositories listed below but many of them are known to explicitly conflict with each other and hence not recommended unless you are a power user and know the technical aspects better.

Mixing third party software repositories

We generally do not recommend mixing a lot of third party repositories since they might conflict with each other causing instability and hard to debug issues. If you are not a technical user, one safer method is to not enable the third-party repo by default and instead use the --enablerepo switch for yum|dnf, or a similar method configurable in the graphical package manager. There are a number of yum|dnf plugins for setting repo priorities or protecting the base packages from being obsoleted by third party repositories which are helpful to more technical users.