Most of the files are sound files, and most trains have much the same set of names. Points to note include the sounds called run0 - run7 which are BVETSS standard, which most trains adhere to and which you should also study before starting to work on sounds. Adhering to BVETSS means that your train will sound right on compliant routes, which is a good thing.
There are also some other files in there:
UKSpt.dll - this is the UK Sprinter plugin from the excellent Simon Gathercole. The plugin adds functionality to your train, allowing for fully-working AWS, TPWS and several other things like door warning lights. There are other plugins - Simon has produced 3 altogether, for Sprinter class DMUs, EMUs and locos. Also, there's a universal one by Oskari, which will do diesel, electric or steam trains.
ats.cfg - this tells BVE what plugin is handling the ATS functions. In this case it contains one line: UKSpt.dll
panel2.cfg - this is the thing that does 'most everything on the train.
sound.cfg - this assigns all those sound files to the actions in the train. some of these actions are native BVE functions, and some are in the plugin.
UKSpt.cfg - this defines the functions of the plugin, including things like engine starting, wiper speeds, and in some cases overload and overspeed functions.
We'll study the various config files listed above later on in detail.
The other really important file is train.dat. This is the file that determines the physics of the train: acceleration, braking, dimensions, weight, etc. Also in here are the motor sounds. As for the config files, that will be studied in detail later.
The other thing (apart from the various readme files, which normally contain copyright data and an introduction to the train) is a directory called D3D. On some trains, this is called BVE4, and if you look in it you'll find that it contains pictures:
These are the images that make up the train view on the screen. It makes life easier to have them in a separate directory, although in fact you don't have to. All the images are Windows/OS2 bitmap format and most people use 256-colour images, which reduceds the file size to 1/3 what it would be if you used 24-bit colour. The good thing about this is that each image can have it's own, dedicated colour palette, so you're not restricted to 256 colours for the entire train. BVE4 will, in fact, work with 24-bit images, but it increases the load on the computer when running the simulation and, provided you use the right palettes for your images, doesn't make a big difference to the quality.
OK. That's a brief look at what goes into making a train. In the next section, we'll have a look at the raw material and software you need to get good results.
On to part 2!