A tendon (or sinew) is a tough band of tissue that connects muscle to bone. It is built to withstand tension. Tendons are similar to ligaments except that ligaments join one bone to another. Tendons and muscles work together, roughly as follows. When muscles contract, the tendon transmits the pull to the bone.
A tendon connects to a muscle at one end, and to bone at the other end. Each tendon has these two "insertions".
Tendons do not create any pulling force of their own. The tendons transfer the force of muscles pulling on the bone. Unlike elastin (another bodily tissue) tendons have very little "give".
Tendons are often connected to joints.