Mathigon notes that studying probability is necessary in order to better understand the likelihood of a particular thing happening. An individual is able to better calculate such likelihoods if he has more information and context about the subject he is attempting to predict.
Probability can be represented numerically with a number between zero and one, with zero representing the impossibility of something specific happening and one representing the certainty of that thing happening. This number is often transferred to a percentage in order to predict something useful, such as a weather person predicting the likelihood of rain on the following day. Such an individual uses probability by taking available data on weather and making the most accurate prediction possible. Probability theory differs from statistics because statistics requires the examination of what has already occurred in order to determine how such a result occurred.
One frequent use of probability is the determination of events that are effectively impossible to quickly predict when a random determination needs to be made. This is commonly seen in sporting events in which a coin flip can influence aspects of the game. In truth, a coin flip can be influenced by factors such as coin speed, but the relative impossibility of using this information to predict which side the coin lands on makes it a useful tool for arbitrary determinations.