Explore the fundamental principles of general relativity in this opening lecture from the Fields Institute's Winter School series, delivered by Zoe Wyatt from the University of Cambridge. Delve into Einstein's revolutionary theory of spacetime and gravitation as part of a comprehensive educational program designed to introduce advanced concepts in theoretical physics. Learn about the mathematical foundations and physical interpretations that form the cornerstone of modern gravitational theory, setting the stage for deeper exploration of relativistic phenomena. Gain insights from expert instruction within the context of the broader thematic program on shocks and singularities in nonlinear evolution equations, connecting general relativity to cutting-edge research in mathematical physics and related fields.