Euler-Bernoulli Beam Theory is a fundamental principle in structural engineering that describes how beams bend under load. It assumes that the beam's cross-section remains perpendicular to its neutral axis during deformation, allowing for simplified calculations of deflection and stress. This theory is applicable to slender beams, where the length is much greater than the height. It provides essential insights into the behavior of structures, enabling engineers to design safe and efficient buildings, bridges, and other constructions by predicting how materials will respond to various forces.