Ley lines are magical emanations of the First World that travel all throughout Golarion. They are the web that connects the two planes together and anchors the First World “behind” that of Golarion.
Most elder fey of both the First World and Golarion know how to use the ley lines to increase their own power and to transport themselves across the world in a blink of an eye. Not all ley lines link to a portal to the First World but many do.
All ley lines link to others via faerie rings, natural creations in various circular sizes by naturally-occurring materials in pristine, untouched areas of the world.
It is common knowledge that ley lines exist, but extremely uncommon for creatures to know how to tap into them and draw their power, and the true purpose they represent. While the ley lines anchor the two planes together by blending their natural characteristics together, the existence of the ley lines is vital to survival for both worlds. They are the source of nature’s magic and their disruption or destruction would have dire consequences for both planes of existence. The fey are generally regarded as their keepers and the most powerful and trusted of them know the secrets of the ley lines. Some mortals, including specially-trained druids, also understand them more intimately.