You've heard of the Lunar Nodes, which mark where the path of the Moon around the Earth intersects with the ecliptic (that is, the apparent path of the Sun from our viewpoint on Earth). These points indicate a conduit of the energy, where we encounter and embrace it into our lives (the North Node) or where we need to let it go (South Node).
In the same way, we can track where the orbits of the planets intersect with the ecliptic. And in the same way, the planet's North Node is where its energy can come into our lives, while its South Node show where we are releasing it or moving past it.
We can track these nodes at their geocentric positions (from Earth's perspective) or their heliocentric positions (from the Sun's perspective).
From a geocentric viewpoint, the nodes of the fast-moving planets (Mercury through Mars) change considerably over time.
By contrast, the heliocentric nodes of all planets (Mercury through Pluto) are almost stationary and change very little over time.
For the outer planets (Jupiter through Pluto and beyond), their geocentric and heliocentric position change little, if at all, over time. For this reason, heliocentric nodes are often used instead of geocentric nodes, because of their stability.
The same symbols for the north and south lunar nodes can be used to represent the north and south planetary nodes as well.