Probability is a measure of how likely something is to happen. When you flip a coin, there's a 50% probability it will land on heads because there are two equally possible outcomes. When you roll a six-sided die, there's a one-in-six probability of rolling any particular number.

Mathematicians express probability as a number between 0 and 1, or as a percentage between 0% and 100%. A probability of 0 means something is impossible, like rolling a 7 on a standard die. A probability of 1 (or 100%) means something is certain, like the sun rising tomorrow. Most interesting probabilities fall somewhere in between.

Understanding probability helps people make better decisions. Weather forecasters use probability when they say there's a 70% chance of rain. Doctors use it to explain how well treatments work. Even game designers use probability to make games fair and fun.

People often misjudge probabilities. If you flip a coin three times and get heads each time, what's the probability the next flip will be heads? Still 50%. The coin doesn't remember previous flips. This is one reason probability is worth studying: it helps people think clearly about chance, risk, and uncertainty in a world where many things are not absolutely certain.