Basically you can either play in campaign or endless mode. in both you are given the choice of 3 regions (U.S.A, Europe and Australia)
In endless mode you can select one of many regions, select difficulty, competitors, year and if you and unlimited money.
In the campaign mode you only have 1 region you can play until you unlock more. each region has a dilemma as you might expect that needs to be resolved within a certain time limit. these may range from getting supplies to build forts or an Olympic village, building a transport route to a hard to reach area or collecting gold from awkwardly placed mines.

The first few scenarios are based around the 1800's and as you progress the time follows suit. And as time presses on new technologies are invented, new transport means are available to you, eg. new trains or new and faster types of train tracks. It's sort of a way to progressively introduce new means of transportations which is very nice.
as you play the game you will realize that certain train stations, bus stops, will need to be expanded or have new facilities added to it. for example you could add more platforms to a train station, make it longer, build a water tower for steam trains, you could add ice cream parlors to get a little more cash off of customers or add a hotel and start raking in the dough.

It is a great game but unfortunately it doesn't include a tutorial. It took me a while to figure out that to rotate things you had to hit the space bar. But, as i said it is a great game, just make sure you read the manual first...