This book presents the reader with basic facts and knowledge of pricing financial derivatives. Also discussed herein is the qualitative analysis and practical methods of their pricing. The extensive expansion of various financial derivatives dates back to the beginning of seventies. The analysis of derivative securities was motivated by pioneering works due to economists Myron Scholes and Robert Merton and the theoretical physicist Fisher Black. They derived and analysed a pricing model nowadays referred to as the Black--Scholes model. The approach was indeed revolutionary as it brought the method of pricing derivative securities by means of solutions to partial differential equations.