Whiteheads and blackheads are both forms of acne caused by plugs of substances, but they differ in appearance and formation. Whiteheads are closed pores clogged with dead skin cells, oil, and sebum, while blackheads are open pores that have been oxidized, making them dark in color. Whiteheads form a white head raised above the skin's surface, while blackheads remain on the skin's surface.