In this chapter a brief introduction to the concept of sliding mode control is given and the properties of sliding mode systems are discussed. The chapter also highlights the benefits of sliding modes when applied to the fields of FTC and FDI. A simple pendulum example is used to introduce the concept. The unit vector approach for multi-input systems, sliding surface design and tracking requirements (integral action and model reference based tracking) are also discussed. The chapter ends with some discussions on the benefits and motivation for sliding mode control in the fields of FTC and FDI.