DNF has been under development for over two years as an experimental package manager that's faster and more versatile than yum. DNF has been available for testing going back to Fedora 18, but with Fedora 22, which will come sometime in 2015, it's likely replacing Yum by default.
DNF is ready for user-testing and has mostly the same CLI syntax as Yum. The advertised benefits include a CLI package manager built on modern dependency solving technology that's faster and less memory intensive, a documented and solid Python API, C bindings, and runs on both Python 2 and Python 3 stacks.
Those interested in learning more about the DNF plans for Fedora 22 (with the Fedora 21 release later this year Yum is still the default with DNF as a separate option) can be found via this mailing list post re-proposing the F22 feature.