A waypoint is a location in the Material Plane where the barriers to other planes are weakened, allowing interplanar travel without the use of spells. In Fellspace, waypoints are typically created by the forceful impact of a comet or meteorite with a planetary body and the associated pulverization of starstuff.
Waypoints can theoretically be made between the Material Plane and any other plane, but it is more common for cosmologically "closer" planes to intersect in this manner, such as the Feywild or Shadowfell.
Waypoints can appear wherever starstuff has been pulverized through a sufficiently powerful impact, as with a shooting star. The effect can be temporary or permanent depending on the amount of starstuff and the severity of the impact event.
In some cases, waypoints can oscillate between open and closed states corresponding with cosmic events such as stellar confluences with related heavenly bodies. Depending on the positions of the moons, stars, and other planets, these oscillations can have periods ranging from a few hours to many centuries.