The concept of probability was introduced as a way of representing our uncertainty about the world. Mathematically, a probability distribution is a mapping from the values of a variable to non-negative real numbers. Semantically, a probability is the chance or likelihood that an event occurs, currently or in the future.
Variables and Their Values
A variable is a mathematical object that takes on values from a certain set, called its domain. For instance, the domain of the variable Sex can be {male, female}. Each variable represents a property of the real world.