The launch image (or default image) is displayed while your app launches. (If no default image is provided, then a black screen is displayed.)
To include a launch image in your app, add images of the appropriate size for the device. In iOS 8 and later, you can create a XIB or storyboard file instead of a static launch image. The launch XIB or storyboard is required to support iPhone 6 sized apps. See the Apple Documentation for more info.
iPad launch images do not include the status bar area. You can provide different launch images for each orientation (Portrait, PortraitUpsideDown, LandscapeLeft, and LandscapeRight); consult the Apple documentation for details.