Learning to see is the foundation of creating realistic art. Many people draw or paint what they *think* they see, and often what we have stored in our mind's eye is a very rudimentary semblance of reality. Learning to see is learning to see things as they really are, and not how you expect them to be.
I teach my students to "find the shapes" in their reference photos and map them out - the outlines of the structure, features, and shadows. How light or dark are they? Can you see each individual hair in a dog's coat or is a smooth gradation? People instinctively "fill in the blanks" with what they think they see, based on their own vague memories.
My mantra has always been "it's not a [.............] - it is shapes and lines, colors, lights and darks. It is not a dog. It is not a cat. It is not a building, or a car, or a mountain. It is nothing. Accepting this and letting go of your preconceived notions allows you the freedom to truly see your reference and recreate it with accuracy.