In simplest terms: the AP art exams have two portions; sustained investigation, and selected works.
The sustained investigation is a series of works that share a theme and are turned in as digital images. Thse 15 images can be completed work, and evidence of research, practice and growth.
The selected works are five works sent in to be viewed (except 3D) show works that best demonstrate skillful synthesis of materials, processes, and ideas, these MAY include selected works.
more on the AP portfolios & submissions process here .