A function is a mathematical tool that assigns an output value to each input value. To put it simply, it takes in an input and produces a desired output. A good example is a calculator: when you type in a number and press the equals sign, the calculator gives you the answer. Functions are used in many areas of mathematics, from basic algebra to complex calculus. They can also be used in computer programming to automate tasks. For example, a computer program might use a function to move a cursor around a screen or to generate random numbers. Fun Fact: British mathematician Alan Turing used functions to break the Enigma code during World War II, which helped the Allies win the war.