Functional relations involving functions with two or more discrete variables appeared long before the introduction of analytical concepts such as a derivative or an integral. Yet renewed interest has only picked up momentum in the last fifty years. Such an active interest is undoubtedly due to the advance of modern digital computing devices. Partial difference equations are a major class of functional relations with recursive structures so that the usual concepts of increments are important. This book describes mathematical methods that help in dealing with recurrence relations governing the behavior of variables such as population size and stock price and will be useful to anyone who has mastered the usual sophomore mathematical concepts. It offers a concise introduction to the tools and techniques that have proven successful in obtaining results in partial difference equations.