Brisket is a cut of meat from the breast or lower chest of beef. It is located in the sternal region, bordering on the shin; and dorsally on the rib cage in the cranial area.
The brisket muscles include the superficial and deep pectorals. As cattle do not have collar bones, these muscles support about 60% of the body weight of standing/moving cattle. This requires a significant amount of connective tissue. So you must cook the resulting meat correctly to tenderize the connective tissue.