The Principle of Least Action is a fundamental concept in physics that states that the path taken by a system between two states is the one for which the action is minimized. Action is a quantity that combines energy and time, and it helps predict how systems evolve over time. This principle applies to various fields, including mechanics, optics, and quantum physics. In essence, the principle suggests that nature operates in the most efficient way possible. For example, when a ball is thrown, it follows a curved trajectory that minimizes the action, demonstrating how systems naturally seek the easiest path. This principle is closely related to Lagrangian mechanics and Hamiltonian mechanics, which are mathematical frameworks used to analyze physical systems.