What is the difference between a bony fish and a cartilaginous fish?

Bony fish belong to Class Osteichthyes, while cartilaginous fish belong to Class Chondrichthyes. Bony fish have a bony skeleton, while cartilaginous fish have one composed mostly of cartilage. Bony fish have body coverings of scales, while cartilaginous fish are covered with dendritical projections (think shark skin).
Bony fish are found in fresh and salt water; cartilaginous fish are found only in salt water. Bony fish have gills covered by an operculum; cartilaginous fish have gill slits. Bony have no eyelids; the cartilaginous fish do. Bony fish have an air-filled swim bladder; cartilaginous fish have an oil-filled liver to keep them bouyant. Hope this helps! Whew!