What problem does trampoline solve and what will the result be?

const trampoline = <T>(fn: () => T | (() => T)): T => {
  let result = fn();
  while (typeof result === "function") {
    result = (result as () => T)();
  }
  return result;
};

const sumTo = (n: number, acc: number = 0): any =>
  n === 0 ? acc : () => sumTo(n - 1, acc + n);

console.log(trampoline(() => sumTo(100000)));