You have your sun sign, the one you probably identify with when someone asks you to name it. This is indeed the most important. It conveys your personality.
But you also have a moon sign, where the moon was located at the time of your birth. This is second in importance only to your sun sign. It represents the inner you, the things that run under the surface, not necessarily the “you” that you present to the world.
So what does it mean if you were born when the moon was in Libra?