The “Permutation” is nothing but each of several possible ways in which a set or number of things can be ordered or arranged. Whereas, “Combinations” can be defined as a selection of all or part of a set of objects, irrespective of the order in which objects are selected. The chapter discusses everything about the Fundamental principle of counting, factorial n. (n!), permutations, combinations, derivation of formulae and their connections along with simple applications.