Recursion is a programming technique where a function calls itself to solve smaller instances of a problem. It is often used to break down complex problems into simpler, more manageable tasks. In a recursive function, there is typically a base case that stops the function from calling itself indefinitely, ensuring that the function eventually terminates. Recursion is particularly useful for problems that have a recursive structure, such as calculating factorials, navigating tree-like data structures, or implementing search algorithms.

Definition: Recursion is a programming technique where a function calls itself to solve smaller instances of the same problem.

For example, a function that calculates the factorial of a number can be defined recursively as the number multiplied by the factorial of one less than the number, with the base case being the factorial of 1. Recursive algorithms are elegant and can simplify code, but they must be used with care, as improper recursion can lead to infinite loops or stack overflow errors if the base case is not properly defined.

Function Factorial(n)
If n == 0:
    Return 1
Else:
    Return n * Factorial(n - 1)

Recursion can be more intuitive for problems like tree traversal (e.g., navigating a binary tree) or solving mathematical problems that naturally break into subproblems. However, iterative solutions may be more efficient in some cases, especially when dealing with large datasets or when the recursion depth is too high. Understanding when and how to apply recursion is a key skill for problem-solving in programming.