Queuing theory is a part of probability theory which has evolved since 1909 by A.K. Erlang. My thesis here describes the importance of queuing theory in business such as of a Call Centre. Call centre provides services to customers and clients in help and they can only receive it by calling the agents and sometimes there are no free agents/servers to facilitate or help them. The part of Call centres which deals with the waiting customers in line and their measures to increase efficiency is known as queuing theory. Queuing theory has proved its way to be one of the major leading factor for organizations as a business point of view.