Kinematic Concept Of Link

Kinematic Link: Each resistant body in a machine which moves relative to another  resistant body is called Kinematic link or element. A resistant body is one which does not go under deformation while  transmitting the force.
Kinematic links can be divided into three types.

1. Rigid link-  In this type of link there is no deformation while                      transmitting the motion. Motion between the piston and crank can be considered as a rigid link.
2. Flexible link- In this type of link there is partial deformation while transmitting  the motion. Belt drive is an example of flexible link.
3. Fluid link-  In this type of link the motion is transmitted with the help of fluid pressure. Hydraulic brake is an example of fluid link.

Credit:- https://www.quora.com/What-is-a-kinematic-link#