Recursion is a programming technique where a function calls itself to solve a problem. It's particularly useful for problems that can be broken down into smaller, similar subproblems, like the Fibonacci sequence, factorial calculation, or tree traversal. Recursive solutions are often easier to write and understand than their iterative counterparts, but they can lead to inefficiencies if not optimized with techniques like memoization. One downside of recursion is the risk of hitting the recursion depth limit or causing a stack overflow, so it’s important to ensure that the recursion has a base case to stop it from running indefinitely.