Recursion Explained: Base Cases, Call Stacks, and How Functions Call Themselves

Recursion is a programming technique where a function solves a problem by repeatedly calling itself with a smaller version of the same input. Every recursive function requires two parts: a base case that stops the recursion and a recursive case that moves the problem closer to that stopping point. Using factorial calculation as an example, each call is added to the call stack until the base case is reached, after which return values unwind back up through the stack. If a recursive function never progresses toward its base case, the call stack fills up and causes a stack overflow error. Understanding these three concepts — base case, recursive case, and call stack — makes recursion significantly easier to reason about and apply.