What is recursion in programming?

Recursion in programming refers to a situation where a function calls itself in order to solve a problem. This approach allows the function to break down complex problems into smaller, more manageable subproblems, usually with a base case to terminate the recursive calls.

When a function is defined to call itself, it typically processes a smaller instance of the original problem, thus approaching a solution step by step. This technique is effective for problems that can naturally be divided into similar subproblems, such as calculating factorials, traversing data structures like trees, or implementing algorithms like quicksort and mergesort.

The concept of recursion relies heavily on the idea of a base case, which stops the function from calling itself indefinitely. This contrasts with the idea of running indefinitely, which would lead to a stack overflow due to too many function calls without resolution.

Recursion is distinct from other programming paradigms that focus on data abstraction, or strategies for optimizing memory usage. While these may be important in their own right, they do not encapsulate the specific mechanism by which recursion operates. Therefore, understanding recursion is essential for solving a variety of algorithmic problems effectively.