Frequency is not equal to probability. According to Bernoulli's theorem of large numbers, when n tends to infinity, the frequency fn(A) approaches the probability P(A) in a certain sense. Probability is a real number between 0 and 1, which is a measure of the possibility of random events. The number representing the probability of an event is called the probability of the event. It is a measure of the possibility of random events and one of the most basic concepts of probability theory.