What is pathfinding?

"For example: 

Player A may want the quickest path (time-wise), so doesn't care about (eg) tolls for crossing the player-owned bridges

Player A may want the cheapest path (eg time is a less important parameter), so wants to avoid toll bridges along the way

Player A may want the safest path (eg getting there is the most important parameter), so wants to avoid nodes where hostile Alliance B is in control, or where more than X casualties have occurred in the vicinity, in the last Y hours.

Player A may want to set his or her own manual waypoints with changing pathfinding preferences along the way - eg pathfind to point A and then to point B (via this major nodal road connection between A and B) and then to point C (but avoiding roads and danger areas whilst you travel to point C)"

Through these possible scenarios, Stormcrow begins to flesh out the means by which Pathfinding wields de facto control over tracts of land: either through the imposition of tolls, or through the threat of potential military conflict and casualties. 

In a follow-up post, GM Thundercat clearly states this, adding: "And of course add into the mix path intersections for interception, ambushes and whatnot...Of course over varying speed terrain - shortest path to intercept, or safest route to interception? Will the interceptors themselves be ambushed? Or the ambushers intercepted by further group moving over the quickest route..."

Checking out the Pathfinding Speculation thread from almost 3 years ago is also a good read.