Here are some examples of coordinating conjunctions in English and what they do:
For
presents rationale ("They do not gamble or smoke, for they are ascetics.")
And
presents non-contrasting item(s) or idea(s) ("They gamble, and they smoke.")
Nor
presents a non-contrasting negative idea ("They do not gamble, nor do they smoke.")
But
presents a contrast or exception ("They gamble, but they don't smoke.")