What Pat said. A Self bow is made from a single stick of wood.
Composite bows are made from several materials, natural or synthetic.
A Tri-lam bow is a composite bow with three layers, each a different wood.
A modern fiberglass bow is a wood-fiberglass composite -- several thin wood strips sandwiched between strips of fiberglass.
A self bow backed with linen, rawhide, flax, sinew, is a composite bow. BTW that backing in many cases is matched to another material on the belly of the bow, making for example a wood-horn-sinew composite