In iOS 7, Apple redesigned the user interface from top to bottom, removing most "skeuomorphic" elements and giving the OS a cleaner and lighter look and feel. Back in January, it was reported that OS X 10.10 -- code named Syrah -- would also see a flatter redesign, but that it would not see as extensive a reworking as iOS did.
This is a concept for Mac OS X Syrah, expected to be published in September 2014. It's based on the new flat design approach of the Contacts and Notes App introduced in Mac OS X Mavericks.
It is not known what Apple will call the next version of its OS X operating system, but may show off the new OS -- and its new California-inspired name -- at WWDC in June of this year. Over the past several years, Apple has tended to release its new Mac operating system in mid-Fall.