Diffraction, diffusion, and effusion are distinct physical processes. Diffraction refers to the bending of waves around obstacles or through openings, while diffusion is the movement of particles from an area of higher concentration to one of lower concentration. Effusion involves the escape of gas molecules through a tiny opening into a vacuum. The discussion emphasizes using resources like Wikipedia and Google for clear definitions and explanations. Overall, understanding these concepts is essential for grasping various scientific phenomena.