The north & south nodes in your horoscope define your life path. Within your horoscope you can find them on which degree they where at the moment of your birth. This is a generational aspects.

They are optical points calculated via your birthdate, hour & place. The nodes are located on the axis. Meaning they contain opposite characteristics. (The signs are 180° apart and oppose eachother, they are in polarity. The opposite end of the axis describe contrary methods of life. The signs experience a pull to one another. They have the contrary quality, frequently uneasy with one another, however they  complement eachother. They push & pull.)

In which signs your nodes are located determines your karmic path, life lessons & blessings.

The north node is what you gain and the south node what you refrain.

Your SN tells you where you are coming from and the NN where you are going to. The SN is what you already know and your comfort zone and the NN is what you are pulled towards too what you'd like to learn/experience from, an unknown territory to develop.

North Node  - Dragon's Head

The knot where you are pulled towards to, to gain experiences in this life to learn from. The sign & house placement tells you which direction. Specifically when these nodes are located conjunct an angle (ASC/DEC, MC/IC) or conjunct planets, they play a significant role in your karmic destiny. It's fated.

South Node -  Dragon's Tale

This is your comfort zone.

It's the opposite of the NN. You have masterd & developped the experiences already (in a previous life).

It's the area what feels safe and goes easy.

It functions as your guideline through life. It plays an important role in relationships with others and during eclips season it will determine fated events when it touches area's in your chart related to them. It then propels you fast forward where you need to be and causes a 'course correct' in your life if that's needed. 
They give you the opportunity to refrain parts of your comfort zone which is outdated and whete you need to say goodbye to, to make place to gain something new to push your forward to grow in life. To define more in depth, you can check the ruling planets of the signs where they are in your chart. These planets play an important role when the nodes are touched!
They are also called the lunar nodes, karmic nodes or dragons head and dragons tale.