Invariants are properties or conditions that remain unchanged throughout a process or operation. In mathematics and computer science, they are often used to prove the correctness of algorithms or to describe the behavior of systems. For example, in a sorting algorithm, the invariant might be that the elements before a certain index are always sorted. Invariants can also be found in physics, where they describe quantities that do not change under certain transformations. For instance, the laws of physics remain invariant under coordinate transformations, meaning they hold true regardless of the observer's perspective. This concept helps in understanding the fundamental nature of various systems.