Permutation is a mathematical concept that deals with the number of different arrangements or orderings of n objects. It is a fundamental part of combinatorics, which is the study of finite or countable discrete structures. Permutations are useful in many fields such as mathematics, computer science, and engineering.
Permutations can be used to determine the number of ways in which n objects can be arranged in a set. For example, if there are three objects A, B and C, then there are six possible permutations: ABC, ACB, BAC, BCA, CAB and CBA. This makes permutation an important tool for solving various problems related to counting and probability.