This paper presents analysis of the effect of actuation on combustion dynamics, Two different categories of actuators are examined: flow sources, e.g., acoustic speakers, and heat sources, e.g,, fuel injectors. These sources are modeled in the conservation equations and a finite dimensional model is obtained. Two methods of analysis are used to gain insight into the physics of actuation, and its stabilizing/destabilizing effect on the combustor through feedback control. The first is the energy method which is used here in a novel way to explain work exchange between the different dynamic components of the system: the acoustics, the flame, and the actuator. Energy analysis is also used to quantify the "useful" and "wasted" work generated by actuators. The second method of analysis is the dynamic method in which the combustor is represented as an oscillator. This method is used as a basis of any optimal control design.