The Photoelectric Effect is a phenomenon where electrons are emitted from a material, typically a metal, when it absorbs light or electromagnetic radiation. This effect demonstrates the particle-like properties of light, as it shows that light can transfer energy to electrons, allowing them to escape from the material's surface. This effect was crucial in the development of quantum theory and was famously explained by Albert Einstein in 1905, for which he received the Nobel Prize in Physics. The photoelectric effect has practical applications in devices like solar cells and photo detectors, making it a fundamental concept in modern physics.