The Riemann Mapping Theorem has significant applications in circuit theory and complex functions, particularly in generating Riemann spheres. It establishes that there are three simply connected Riemann surfaces: the plane, the disc, and the sphere. This classification leads to a division of surfaces into parabolic, hyperbolic, and elliptic types based on curvature. A key application is in understanding entire functions; for instance, if an entire function omits two points, it can be shown to be constant using the theorem. Overall, the Riemann Mapping Theorem is crucial for classifying surfaces and analyzing complex functions.