Exact Results in Quantum Theory

We would like to introduce D-branes and make various remarks on string theory amplitudes and their relations to mathematics in type II string theory in which getting the exact and final form of the world sheet integrals up to five point mixed closed-open amplitudes to all orders are given.We are also going to to talk about all kinds of effective actions involving DBI, Chern-Simons and more importantly new Wess Zumino actions. Indeed we try to provide a comprehensive explanation even for D-brane-anti D-brane systems. We also introduce various new techniques to be able to derive all order α’ corrections to all type II super string effective actions. If time allows, we then mention several issues related to those effective actions as well.