OS X Yosemite with all of its new features and user interface changes was shown off at the Keynote at WWDC 2014 this afternoon.

It was announced that the operating system would be available starting today for developers as a Developer Preview version, but that it would be released to the public in the Fall of this year.

More importantly, just like OS X Mavericks, OS X Yosemite is going to be a free upgrade for OS X users.

There are a number of improvements in OS X Yosemite, including Continuity, SMS/Phone calls, a brand new SpotLight Search, improvements to Safari, iCloud Drive, E-mail Markup, and much more.