Quick
A composite function is a function of a function. A composite function consists of an outside function and an inside function.
Details
Say there's a function y = f(x) = x + 3 and another function x = g(t) = t2 − 2t. Then the equation for the function g(t) can be substituted for x in the function f(x) to result in y = f(g(x)) = g(t) + 3 = f(x) = t2 − 2t + 3. y is now a function of a function, or a composite function. f is the outside function and g is the inside function.