What Is Yang & Yin?

I have downloaded astrolog...nice program. Still learning it (I finally figured out how to save stuff..yes!). So I was looking at what's happenin now up there in the sky..Moon's in Cap. So I looked at the bottom and it gives alil summary...like fire: 5, earth 5, air 5, water 7, then it says something about yang: 10, yin: 12.

What are yang and yin?? Why is it important? Does anyone know??

~Much Love~
~Sarah~

A short summary:
Yang = Fire + Air, the 'active' elements.
Yin = Water + Earth, the 'passive' elements.
Some also use the terms masculine and feminine, but I'm not really fond that useage because they don't tell the whole story. Yang is lika a hot summer day, while Yin is like a cold winter night. And before you say that Yang seems better than Yin, consider this: Which one gives you your dreams? Which one allows you to see the stars?

I agree with C.N. about using the terms 'masculine' and 'feminine'. I'm also wary about using the terms 'positive' and 'negative' which are sometimes mentioned. Although these terms don't have a perjorative meaning - they are more like positive and negative terminals on a battery - they can easily be misinterpreted.

Yin Yang forms a whole - both are needed for completeness,