How does ExecutorService.submit work

I am trying to understand how Executor.submit(Runnable) works. Suppose we create a thread pool of size 2 using ExecutorService.

We have a class called Runner implements Runnable.

ExecutorService.newFixedThreadPool(2);
for (int i = 0; i <5; i++){
  ExecutorService.submit(new Runner());
}

When we do new Runner() are we not creating 5 threads already?

So how does ExecutorService help in this case?