In the simplest relaying networks, one intermediate relaying node is introduced that supports the communication from the source to the destination, where the relay has the alternative to simply forward an amplified version of its received signal (Amplify-Forward "AF") or to estimate the source message by hard decision and transmits it to the destination (Decode-Forward "DF"). Enormous amount of literature is devoted to theoretical investigations of such relaying networks based on information theory. In this work, the analysis is extended to a two-way relay channel (TWRC), in which both terminals have information to exchange with each other via the relay. To this end, the theoretical analysis for the capacity of such a TWRC will be carried out systematically based on the-state-of-the-art in this field.