A minimalistic UI designed to be functional, yet also efficient and elegant.
History
RealUI was originally created by Nibelheim aka Real, and published on WoW Interface during the Wrath of the Lich King expansion.
Towards the beginning on Mists of Pandaria, some struggles in real life prevented Nibelheim from continuing to update the UI. Due to this, Gethe volunteered to fix RealUI so that it could at least survive the expansion launch.
While Nibelheim was able to come back for a bit after MoP launched, and made a fairly significant overhaul in that time. By the time Warlords of Dreanor came out though, real life had come around again and forced Nibelheim away for the game. At that point Gethe was given control of RealUI, and has been maintaining it ever since.