This paper addresses a brief introduction on various extensions of process algebra for concurrent and communicating systems as an area of research in concurrency theory, the theory of parallel and distributed systems in computer science. Literature has tracked the growth of process algebra since CCS (Calculus of Communicating Systems) was formulated till RCCS (Calculus for reversible concurrent systems), in order to reflect the changes in computing environment and comparison has been sketched on the basis of this. A relationship between concurrency and communication has been explored in this literature. Literature presents some analytical reasoning on this matter. In this paper, present situation and current trends in process algebra is also considered and makes a reason why some models are being preferred for extensions by researchers over others. Some challenges for the future work are also mentioned in this literature. © 2012 IEEE.