"Soda" and "Pop" are interchangeable terms for "Soft Drink" (carbonated drink not containing alcohol). The western part of the united states normally refers to it as "Pop" while the eastern refers to it as "Soda" "Coke" is short for "Coco-Cola" which is a brand name for a "Cola" drink, although some people use "Coke" as a generic term for "Cola".