'Glucosamine is one of several 6-carbon amino sugars found in the body and is a building block for glycosaminoglycans. The exact mechanism of action of glucosamine, other than enhancing the natural cartilage repair process, is unknown.
Chondroitin is a molecule that occurs naturally in the body. It is a major component of cartilage -- the tough, connective tissue that cushions the joints.'
'Chondroitin helps to keep cartilage healthy by absorbing fluid (particularly water) into the connective tissue. It may also block enzymes that break down cartilage, and it provides the building blocks for the body to produce new cartilage.'
They are often sold as a compliment to each other or can be taken alone of course, do a Google search on them for more detailed information.
Good luck hombre ...