Cologne is a type of perfume, a liquid that smells good and is meant to be dabbed behind your ears. When you get dressed up for a night on the town, you might be sure to put some cologne on your neck.
Both men and women wear cologne, which is scented with extracts or oils in a base of alcohol and water. Cologne is considered a kind of toilet water, which is less concentrated than perfume — and can be applied more liberally. If you've ever stood in an elevator with a man wearing an excessive amount of cologne, you know there can be too much of a good thing. The word is from the French eau de Cologne, "water from Cologne (Germany)."