Diet and Regular colas.
They are the same in they come in a variety of fizzy flavors. They make you burp and are refreshing on a hot summer day and go down nicely with fries and a hamburger. They mix well with alcohol --except vodka and scotch.
Both will burn holes in your stomach if you drink too much and are not good for your teeth.
The difference is that there are less carbohydrates and sugar in diet pop making it possible for dieters and diabetics to enjoy pop and not endanger themselves in doing so. I prefer diet drinks as I am diabetic and I really don't miss regular cola.