Both words are used to talk about the different ways we use our eyes. ‘Seeing’ is a physiological process, it is something that our eyes do automatically. When you ‘see’ something, it is not intentional, but accidental. On your morning walk, you may see a cute little puppy, a man wearing a pink shirt, and an old motorcycle parked next to your new car. When you went for the walk, it was not your intention to see all these objects. You saw them because they came in front of you. You couldn’t avoid noticing them.
‘Looking’, on the other hand, is an intentional act. When you look at something, you pay attention. For example, if you look at a puppy, you observe it carefully. You begin to pay attention to its colour, size, etc.