Hello Vimal
Policing and shaping are QoS techniques that are used to enforce lower bit rates than what the physical interface is capable of. Shaping will buffer traffic that goes beyond the allowed bit rate, while policing will drop packets that exceed the bit rate.
If packets are buffered during shaping, then this means that buffered packets will be delayed in their traversal of the network. This will only occur if the enforced limit is reached. If traffic rates are below the enforced limit, no latency will occur.
The results of policing are even more severe. If packets are dropped, then other error correction mechanisms (such as those used with TCP) will have to kick in at higher layers to have the lost packets resent. This brings about even more delays. If UDP is being used, packets are lost for good resulting not in latency, but packet loss.
You can find out more about shaping and policing at the following lessons:
I hope this has been helpful!
Laz