eat : to take into the mouth and swallow for nourishment
dine: to entertain at dinner
The main difference between eating and dining, is that eating is a necessity while dining is an art. One eats to survive, to obtain the nourishment that he or she needs to sustain their bodily needs.
Dining, on the other hand, isn't that simple. It is not just a simple process of putting food into your mouth, chewing, then swallowing it. Dining is a package. This package includes the ambience, the service the staff provides, the company, and of course the décor. Only when all this comes together, will dining be a pleasure. Anything less, and the experience would be what I deem as incomplete.