Bursae are small, fluid-filled SACS that are found in the body. They are located between tendons and bones and act as cushions to reduce friction and provide lubrication. The term 'bursae' is derived from the Latin word for purse, and they are also known as SACS. SACS is an acronym for synovial-associated capsule, which is a type of bursa. Synovial-associated capsules are found in joints and help to reduce friction between the bones and tendons.