Instantons are solutions to the equations of motion in field theory that represent localized, finite energy configurations with topological charge. They play a crucial role in theoretical physics, particularly in quantum field theory, quantum chromodynamics, and string theory. Instantons have important applications in various branches of physics, such as understanding non-perturbative effects, tunneling processes, and symmetry breaking. They are also used to describe phenomena like the strong nuclear force, tunneling in quantum mechanics, and the formation of topological defects in condensed matter physics.