There are many communication theories and they did not come on the picture in the twentieth century but for the first time Aristotle addressed the issues of communication. He presented the model of communication which had three main concepts including speaker, message and listener. He presented the communication theory which deals with the concept that what is the communication process when an orator is speaking with a large audience. The second communication theory is the Lasswell’s Model, which also introduces the concept of medium that comes between the message and listener. Other relatively developed theory is of Shannon & Weaver’s Model, which has also introduced some other concepts which facilitate or hinder the communication process. Some other theories include Schramm's Model, Westley-MacLean model and Kincaids's Convergence. I think among all the communication theories Schramm's Model is the detailed and the best one because it also gives the process of encoding and decoding.
For complete details: Communication theories
For complete details: Communication theories