Everyone knows what their 'sign' is, but do you know what it means?

The fixed stars are stars that are so far away that they always appear in the same position in the night sky, and rotate above us as if on a spherical shell with the earth at the center. Of course it is the earth that rotates, but the perception is of a rotating star field.

Because the earth orbits the sun, which is much closer, the sun appears to move through the star field, a trip that takes one year. What part of the sky the sun was in at your birth defines your 'sun sign'. Similarly, where the moon was at your birth becomes your moon sign, and where the wandering planets defines what 'houses' rule your sign.

Because of something called the 'Precession of the Equinoxes', the signs are gradually shifting; roughly every two thousand years, the sun progresses through one sign and is entering the next sign when it used to enter the previous one. Since the signs were defined about two thousand years ago, the signs are actually off by one, and you may find your neighboring sign more closely aligned to your life.