Explain the follwing quote from "A Clean, Well Lighted Place": "We are of two different kinds."

The two
waiters of 's " " converse after the old man has been told by the younger waiter that
he must go home.  This younger waiter is eager to go home to his wife, but the old man has
wanted to stay, and the older waiter understands why; hence he tells the younger man, "We
are of two different kinds."  For, while the younger...