unity what is a coroutine code example

Example 1: unity coroutine

void Start() {
  StartCoroutine("func"); // Start coroutine named "func"
}

IEnumerator func() {
  Debug.Log("Hello");
  yield return new WaitForSecondsRealtime(1); //Wait 1 second
  Debug.Log("World");
}

Example 2: how to start a coroutine in c#

void Start()
    {
        StartCoroutine(Test());
    }

    IEnumerator Test()
    {
        yield return new WaitForSeconds[2];
    }