JavaScript uses two main methods for defining a function: Function declarations (sometimes referred to as function statements) and function expressions. The main functional difference between these two methods is that function declarations are hoisted, meaning you can invoke the function even before it has been defined. Function expressions are not hoisted.

These two methods were covered in the Getting Started course for this series, but if you feel you need a review, take a moment and view this YouTube video I produced a while back explaining both methods in detail: Function Declarations VS Function Expressions in JavaScript