This paper provides an introduction to the problems of control of plasmas and plasma magnetic-confinement devices known as tokamaks. The basic science of fusion plasmas and objectives of plasma magnetic-confinement technologies are described. In addition to a general overview of plasma control problems, more extensive discussions of three specific classes of problems - control of plasma magneto-hydrodynamic behavior, control of plasma parameter internal distributions, and methods for handling system faults or unexpected loss of control - are provided.