Diploblastic animals are those which have 2 germ layers - the ectoderm and the endoderm. Lower animals like the sponges and cnidarians are diploblastic. Compare them to humans and other higher animals, which have three germ layers - ectoderm, mesoderm and endoderm.
The Bilateria /ˌbaɪləˈtɪəriə/ or bilaterians, or triploblasts, are animals with bilateral symmetry, i.e., they have a head ("anterior") and a tail ("posterior") as well as a back ("dorsal") and a belly ("ventral"); therefore they also have a left side and a right side.
Both protostomes and deuterostomes belong to kingdom Animalia, subkingdom Eumetazoa, which consists of animals having three germ layers and bilateral symmmetry, Clade Nephrozoa. Protostomes, deuterostomes and Xenacoelomorpha are also members of clade Bilateria which is comprised of animals made up of bilateral symmetry .