they are sounds made by a person during sex to express their feelings. most of the time they moan of pleasure but sometimes its of pain also. sometimes when you moan you get more pleasure that when not expressing any feelings.
Everyone is a little different, but it always carries the same sexual tone which you will know once you hear it. It can take the form of grunting, heavy breathing, or louder, more drawn out noises.
By being human. All humans are sexual. Unless you mean how can you be sexy? In which case, that is relative. Each individual finds "sexy" to be different. It's mainly about confidence.
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