Probability theory is a branch of mathematics that deals with the study of random events and the likelihood of their occurrence. It helps in quantifying uncertainty and making informed decisions based on uncertain information. Probability theory is used in a wide range of fields including statistics, finance, engineering, and physics to analyze and model random phenomena. It involves concepts such as random variables, probability distributions, and the laws of large numbers. The goal of probability theory is to provide a framework for understanding and predicting the outcomes of uncertain events.