.STORYBOARD File Extension
File TypeInterface Builder Storyboard Document
What is an STORYBOARD file?
Developer file introduced with Xcode 4.2, an IDE used for creating Mac OS X and iOS applications; stores screen layouts for an application as well as the ways the screens interact with each other through application events.
Interface Builder storyboards provide a drag and drop interface for connecting view functions in an application. This allows developers to link views visually without having to write source code.
NOTE: Interface Builder is a component installed with Xcode.