What is the difference between a crown and bridge?

A crown is used to cover an existing tooth, while a dental bridge is used to fill in the space or gap caused by one or more missing teeth.  In its most simple form a bridge is made up of a false porcelain tooth (pontic) that is held between two porcelain crowns (abutments).  The abutments are placed over the existing teeth on either side of the gap in your smile, functioning as anchors for the false tooth.