Diffraction occurs when light rays are scattered and change direction as they pass through a small aperture or close to an opaque edge. In photography, this effect is most noticeable at small lens apertures, where it can slightly reduce sharpness by spreading the light across the image.
While a natural part of optics, diffraction is important for photographers to understand because it influences the balance between depth of field and image clarity. Controlling aperture size carefully allows photographers to achieve the desired focus and maintain optimal sharpness in their images.