A dutch braid is a three-strand braid where strands are crossed under instead of over the middle strand. It is sometimes called an inverted braid, an upbraid, or an upside-down french braid. Dutch braids can be done on any hair that will hold a french braid.
Dutch braids are extremely versatile. Their "outward" appearance makes them ideal for creating raised styles, and their simplicity makes them easy to manipulate in a variety of ways.
For instructions on how to do a dutch braid, see the DreamweaverBraiding site here.
For more pictures of dutch braids I've done, see the Flickr set here.