CAF - Core Audio Files
Core Audio Files is Apple's file format for audio made ready for playing by applications on iOS and OS X.
QuickTime Player and Finder play CAF files directly. They are the modern version of 'snd ' resources and AIFF files, and can be expected to be embedded in casual and proprietary file formats where interchangeability is not a priority.
File Juicer can extract them, should you be interested in using them anyway. Or if you are just curious to hear what sounds may hide inside a file of rarely used type.
Wikipedia on Core Audio Format
Safari can play caf files linked from web pages with the html5 audio tag. Below I have only included the .caf version so you discover if your browser does not support it. Such use of core audio files only makes sense if you know that it is Safari which will display your content, like if you use WebViews in your iOS or OS X app.
This is the markup used for embedding the Sosumi.caf file