The Train List window shows you all the trains currently present in your control area. From here, you can instruct trains to run to a different timetable, pass signals at danger where necessary, or even - if you're in a real mess - reduce their length or remove them altogether.
To perform an action on a particular train, right-click on it in this list and select from the menu. See below for details.
ID - This is the train description. Note that the train list shows the real reporting number of any trains; if you get into trouble with the train describer - for instance if you have lost track of what a train is - you can usually find out the information you need here
Timetable - This is the reporting number of the timetable the train is running to. Usually the same as the reporting number but if you have to replace one train with another, this might be different.
Dir - The direction the train is heading: in most cases, Up = towards London; Down = away from London.
Status - Shows the current speed or status of the train
Current/Prev Location - This shows the description of the last named location the train passed - usually the last station passed
Length - the length of the train
Can pass sig - is “Y” if you have authorised the train to pass a signal at danger
Non-stop - is “Y” if you have told the driver to pass through the next station non-stop
Power - indicates the power required by the train. Can be e.g. Diesel, AC (for overhead lines), 3DC (for 3rd rail) or 4DC (for LUL 4th Rail)
Description - shows the description of the timetable the train is running to
By right-clicking on a train you can bring up a menu which allows you to perform various actions on that train.