Basically, turn the video game “Transport Tycoon” into a simplified board game.
Everyone starts with their own tiny, unconnected town. You start earning money by moving the few passengers/goods that are present in your town. This allows building longer roads and railroad tracks. You will connect to the cities of other players over time, starting some trading and cooperation. Most resources on the map can only be claimed by one person; most cities on the map can also only belong to the first person who connected to it.
In that sense, everyone is building towns across the whole country + infrastructure, trying to eventually own the largest piece of the pie.