Young's Modulus is a measure of the stiffness of a material. It quantifies how much a material will deform under stress, specifically tensile stress, which is the force that pulls the material apart. The higher the Young's Modulus, the stiffer the material, meaning it will stretch or compress less when a force is applied. This property is crucial in engineering and materials science, as it helps determine how materials will behave in different applications. For example, metals typically have a high Young's Modulus, making them suitable for construction, while rubber has a low Young's Modulus, allowing it to stretch easily.