On your first day as the new Chief Operations Manager for a major railway, your expectations of sitting back in a nice office carefully planning generic train routes and timetables turn out to be completely wrong. In your new company, trains don't follow a schedule - they just drive on and on, whereever the tracks send them. A very laid back approach, but the traditional stuffy and bureaucratic way has two major advantages: fewer collisions and more reliable customer service. It's your job to still ensure both - by operating the switching points.
There are seven different track networks (i.e. seven levels), each of which has to be 'solved' with five combinations of trains. Trains can't be controlled directly - you can just tell them to stop at the next station (to pick up passengers there). The letters A to Z on the keyboard are assigned to the different switching points. Pressing them will change the respective direction. This way, the trains are diverted to (hopefully) collision-free routes which service all the stations sufficiently.
The obvious way to lose the game is train disasters, the other one is angry customers. If you let passengers wait for too long, they become white with rage and start hijacking trains. And if a station gets so packed that passengers have to go home again, because they can't even enter the platform, you lose a life (aequivalent to a train crash). The goal of every level is to safely transport 25 passengers.
All this might not sound like much, but with up to three trains moving at the same time (and the occasional goods train being diverted through your network), taking into account their different speeds and the arrival rates of passengers at the stations, it is a really hard task to keep an eye on everything. Coordination skills which don't overload in stressful situations are a prerequisite, but the primary requirement is actually a more subtle one: intimate knowledge of the keyboard. The Train Game will turn you into a master typist and it'll entertain you very well along the way - forget about all those 'learn to type' programs!