Your astrological Sun Sign (as in "What's your sign?") is easy to find because man conveniently constructed calendars based on the motion of the Earth around the Sun, with one "year" defined as the time for one revolution. The Sun appears (from Earth) in nearly the same position (degree) in the same zodiac Sign on the same day each year - which makes it easy to guess what Sign the Sun is in by referring to ranges of dates. But for the Moon and Planets, there is no such simple correspondence. Their positions must be calculated by computer, or by hand using tables (ephemerides) in a book called an Ephemeris.

The Sign the Sun was in at the time of your birth indicates your basic nature and the "strategies" you favour in dealing with life situations. Signs are associated with "strategies" while the Sun and Moon and Planets represent various aspects of your psyche. The Sun represents your "sense of self" or "essence" or "character" and things related to the center of your being. Character is not the same as personality - nor is how you see yourself necessarily the way you appear to others. This is why some "traits" you hear about a Sun Sign may not seem true for someone - for they are really about their inner being, not their outer personality.