How does that differ from, say, the function (or work/duties) of a bus driver, a teacher, a waiter, a lawyer, and so on?

1. In his Ethics, Aristotle speaks of the function (or work) of a human being. What is that? How does that differ from, say, the function (or work/duties) of a bus driver, a teacher, a waiter, a lawyer, and so on? Discuss this interesting point. In other words, what does it mean to be a human being? What do we have to do in order to be decent human beings?
2. What is the relationship (similarities and differences) between Heraclitus and Parmenides. What is the main point of the Atomists?