Raku is a type of method for making pottery. The process involves special firing in two phases that creates one-of-a-kind pieces. The pottery is named for a palace in Kyoto.
My sculptor sister uses raku decorating for her pieces. Pottery is fired at a low temperature and then moved while hot to a container with combustible materials (as paper or sawdust) that catch fire and cause a reaction creating various colors and patterns in the pottery's surface. I can find no information on a decorating style by that name.
Raku is a form of Japenese pottery and is used in the Japanese tea ceremony. It usually is in the form of hand molded clay bowls, which are fired at low temperatures. Because they are hand molded they are one of a kind. Often they will have pine boughs and interlocking circles sketched on them.