What is the concept of recursion in programming?

Recursion in programming refers to a method where a function calls itself to solve a problem. This concept is particularly useful for breaking down complex problems into smaller, more manageable pieces, which can be solved individually. The ability of a function to invoke itself allows programmers to design algorithms that can easily handle tasks such as navigating data structures (like trees or graphs) or solving mathematical problems (like calculating factorials or Fibonacci numbers).

When a recursive function is executed, it usually includes a base case that stops the recursion once a condition is met. Without this stopping condition, the recursion would continue indefinitely, leading to a stack overflow. Recursive solutions often provide a clear and elegant way to tackle problems that benefit from such a divide-and-conquer approach, making them easier to understand and implement in many scenarios.

The other options describe different programming concepts. For instance, loops iteratively repeat code rather than relying on self-invocation like recursion. Design patterns focus on structured solutions to common problems but are not directly linked to the functionality of recursion. Variable nesting pertains to the scope and accessibility of functions and variables within different contexts, which does not specifically address the self-referential nature of recursion.