Train Simulator (originally RailWorks) is a train simulation game developed by Dovetail Games. It is the successor to Rail Simulator, and was released online on 12 June 2009 and in stores on 3 July 2009.
The first release of RailWorks contained all five real-world routes of the original European and North American releases of Rail Simulator, and added three new fictional routes: a large UK goods yard, a route set in the Alpine region and a route based around Denver, Colorado.
It is a Steamworks title, which means it uses and requires Steam to activate and to deliver core game updates. Steam is used to deliver additional routes and locomotives in the form of downloadable content. The core game has received several updates since release, including major new versions RailWorks 2: Train Simulator, RailWorks 3: Train Simulator 2012, Train Simulator 2013, Train Simulator 2014, Train Simulator 2015, Train Simulator 2016, Train Simulator 2017, Train Simulator 2018 and Train Simulator 2019 released between 2010 and 2019, respectively.
Source: Wikipedia, "Train Simulator (video game)", available under the CC-BY-SA License.