If your understanding of Calvinism was learned in a normal CofC setting the odds are high that what you heard was a caricature of Calvinism; and that makes it difficult to explain to another person. As an example, a person I respect very much was quoted on this blog as deriding Calvinism in one sentence and praising Augustine in the next. Go figure!

Perhaps the briefest way to explain Calvinism is to simply say it is the belief that this is God’s world and he runs it the way he wants. He is not thwarted by mere men and women nor does he ever have to resort to plan B. That is actually a pretty simple summation.
Peace,
Geezer