Your SUN SIGN is the sign you're probably aware of. This is the sign you'd tell someone if they asked "What's your sign?". BUT--most people do not know they have more than just their sun sign. Your moon and rising/ascending sign also play a huge part in people's personalities--debatably more so than the SUN SIGN.
Your SUN SIGN is determined by the date of your birth, which is why most people know their SUN SIGN (most people know their birthday). The SUN SIGN could be said to be your personality. It's the way you handle situations, make decisions, and interact with the world in general. It could be said to be the most basic part of who you are.
If you aren't sure which sign matches up with your date of birth--click on either "Aquarius - Cancer" or "Leo to Capricorn" above, find your birthday, then read about YOUR SUN SIGN!(You can calculate your SUN, moon, and rising sign ANY TIME at my favorite website here.)