Chapter 1 is for readers who have less background in partial differential equations (PDEs). It contains materials which will be useful in understanding some of the jargon related to the rest of the chapters in this book. A discussion about the classification of the PDEs is presented. Here, we outline the major analytical methods. Later in the chapter, we introduce the most important numerical techniques, namely the finite difference method and finite element method. In the last section we briefly introduce the level set method. We hope the reader will be able to extrapolate the elements presented here to initiate an understanding of the subject on his.