The Pigeonhole Principle is a simple concept in mathematics that states if you have more items than containers, at least one container must hold more than one item. For example, if you have 10 pairs of socks but only 9 drawers, at least one drawer will contain more than one pair of socks. This principle is often used in combinatorics and probability to demonstrate that certain outcomes are inevitable. It can be applied in various fields, including computer science and statistics, to solve problems related to distribution and organization of data.