Ares is the god of war in Greek mythology — the one who stands for fighting, blood, and battle itself. In the old stories he is strong and fierce, but not especially wise; the Greeks often liked Athena, who is clever in war, more than they liked him. The Romans told similar stories about a war god, but they called him Mars, not Ares. Though actually, Mars later became a calmer, more official figure in Rome (the planet and the month March remember him), while Ares stayed closer to the raw mess of fighting. This is a name from myth, not a word you use for a person in the street.