Settlers 1/2 are logistics simulators. The core of gameplay is that the map consists of vertexes on which you can place flags, and then connect flags with paths. On each path there will be exactly one porter, who will carry stuff from a flag to another. Arranging your network so that goods get where they are going in a reasonable time is like 90% of the gameplay.

It's been a while since I played these games. With settlers 1 and 2, a major portion of the game was managing the transport of resources. That meant setting up strict pathways and even blocking some resources from going down some paths to setup a "priory" route for shipping important goods.

I believe Settlers.. 3? got rid of that completely. Instead of manually placing paths and controlling the shipping routes the game would just figure it out for you.