What functional technique does this code implement and what is its main benefit?

const memoize = <T extends (...args: any[]) => any>(fn: T): T => {
  const cache = new Map<string, ReturnType<T>>();
  return ((...args: Parameters<T>): ReturnType<T> => {
    const key = JSON.stringify(args);
    if (cache.has(key)) return cache.get(key)!;
    const result = fn(...args);
    cache.set(key, result);
    return result;
  }) as T;
};

const factorial = memoize((n: number): number =>
  n <= 1 ? 1 : n * factorial(n - 1)
);