Chern-Simons Theory is a topological quantum field theory that arises in the study of three-dimensional manifolds. It is named after mathematicians Shlomo Chern and James Simons, who developed the mathematical framework for this theory. The theory is characterized by a Chern-Simons action, which is a specific type of integral that involves a gauge field and its curvature. This theory has applications in various areas of physics, including string theory, quantum gravity, and condensed matter physics. It provides insights into the behavior of topological phases of matter and has been instrumental in understanding phenomena like anyons and quantum Hall effects.