When one body (normally rigid) moves relative to other it is known as link or Kinematic link.
There are following types of links.
1. Rigid link: Which does not go under deformation while transmitting motion. Example – Connecting rod.
2. Flexible link: Which deforms partially while transmitting motion. Example – Belt drive.
3. Hydraulic or fluid link: In which the motion is transmitted through fluid. Example – Hydraulic brakes.