Physical evidence can be classified into various types, including biological, trace, impression, and firearms evidence. Biological evidence includes DNA samples, bloodstains, hair, and bodily fluids. Trace evidence includes fibers, glass fragments, and paint chips. Impression evidence includes shoeprints, tire tracks, and tool marks. Firearms evidence includes bullets, shell casings, and gunpowder residue. Each type of evidence can provide valuable information to investigators and help solve crimes.