Morality...

# concern with the distinction between good and evil or right and wrong; right or good conduct
# ethical motive: motivation based on ideas of right and wrong

In a couple of threads I have seen the word "moral" tossed around but even in context I have no firm idea what the speaker means.

How does a non-believer decide what is right or wrong. Even more interesting, can an Atheist have a concept of good and evil?