Noether's theorem is a fundamental principle in physics and mathematics that connects symmetries and conservation laws. It states that for every continuous symmetry in a physical system, there is a corresponding conservation law. For example, if a system is symmetric in time, it conserves energy; if it is symmetric in space, it conserves momentum. This theorem was formulated by the mathematician Emmy Noether in 1915 and has profound implications in various fields, including classical mechanics, quantum mechanics, and field theory. It helps scientists understand why certain quantities remain constant in physical processes, providing a deeper insight into the nature of the universe.