In order to transmit motion, the driver and the follower may be connected by the following three types of links.
1. Rigid Link: A rigid link is one which does not undergo any deformation while transmitting motion, strictly speaking rigid links do not exists. However, as the deformation of a connecting rod, crank etc of a reciprocating steam engine is not appreciable, they can be considered as rigid links.
2. Flexible Link: A flexible link is one which is partly deformed in a manner not to effect the transmission of motion. for example: Belts, ropes, chains and wires are flexible links and transmits tensile forces only.
3. Fluid Links: A fluid link is one which is formed by having a fluid in a receptacle and the motion is transmitted through the fluid by pressure of compression only, as in the case of hydraulic press, jacks and breaks.https://www.engrz.com/2013/12/11/types-of-links/Mechanical Engineering