Even if you never expect or need to take a course in Calculus, having a strong liberal education should include understanding some of the most basic concepts in science. The cornerstone of today's high tech, big data world is Calculus. It is the language and foundation of modern statistics, engineering, physics, chemistry, medicine, quantitative finance, and the list goes on. So if you have always felt that this subject was complicated then this article is here to answering in the simplest terms: What is Calculus?