This monograph discusses the current state of several applications and provides theoretical methods and tools for their investigations. Plasma theory is presented as a modern discipline of theoretical physics. The main emphasis is on classical plasmas as used for laser-created plasmas, plasmas for magnetic fusion, nonlinear waves, as well as important in astrophysics. Even though the role and importance of plasma physics has been increasing, only a very few existing books attempt to treat plasma physics as an advanced course in theoretical physics. In addition, modern theoretical physics provides tools necessary for analyzing nonlinear phenomena in plasmas. This work will fill this gap.