One of the first and most important examples of "poker math" that new no-limit hold'em players need to learn is how to calculate "pot odds." In fact, when people talk about the "math of poker," a lot of the time they are mostly referring to pot odds and how an understanding of them can help you decide whether to bet, raise, call, or fold.
Put most simply, pot odds represents the ratio between what you stand to gain in a hand of poker and what you have to spend in order to get it — that is, the ratio between your reward and your risk when making any given decision during a poker hand.