Ackermann's Function is a classic example of a recursive function that is not primitive recursive. It was developed by Wilhelm Ackermann in the early 20th century to illustrate the concept of computability. The function takes two non-negative integers as input and produces a single non-negative integer as output, growing extremely quickly with even small inputs. The function is defined using a set of rules that involve recursion, making it a useful tool in theoretical computer science. It serves as a benchmark for measuring the efficiency of algorithms and helps in understanding the limits of computation, particularly in relation to Turing machines and computability theory.