Function composition is a mathematical operation that combines two functions to create a new function. If you have two functions, f(x) and g(x), the composition of these functions is written as f(g(x)). This means you first apply the function g to the input x, and then take the result and apply the function f to it. In simpler terms, function composition allows you to chain functions together. For example, if g(x) represents doubling a number and f(x) represents adding three, then f(g(x)) would first double the number and then add three to the result. This process can be useful in various fields, including mathematics, computer science, and engineering.