The South Node, sometimes called the "Dragon's Tail," is the intersection point where the moon's orbit crosses the sun's path from North to South. The South Node is exactly 180 degrees away from the North Node, in the opposite Zodiac sign.
It expresses your karma, or the lessons you need to learn from your past life. If you do not believe in past lives, you can consider this point to be lessons that you need to learn, or challenges to overcome, from childhood.
The South Node also gives you hints as to talents that you brought into this life. The South Node is a bit of a “double-edged” sword. On one hand, you have talents in the sign of the South Node. On the other, you need to use those talents to move to the sign of your North Node.
For example, if your South Node is in Sagittarius, you may have spent many past lives developing wisdom while meditating in a mountain cave. In this life, you may not want to come in to the world from your peaceful mountain. However, you must step into the opposite sign Gemini North Node to do your work in this life. A Gemini North Node person would need to communicate all of that past life Sagittarius wisdom to the world during this lifetime.