If you are fearless, you are not afraid — or you act as if you are not. It is an adjective, usually praise: a fearless reporter, a fearless climber. It can also sound a little reckless: a fearless driver who does not slow down. People stretch it away from real danger: “fearless” honesty, “fearless” fashion, meaning bold, not “this person feels zero fear.” Though actually almost nobody feels no fear at all; we still call someone fearless when they go ahead anyway. It is ordinary English, a bit warm and admiring, fine in speech and writing. The opposite feeling is often fearful, but fearful can also mean “causing fear,” so they are not a perfect pair.