Ok so I have to confess that I literally don’t know anything about trains, just that I like them and watch them when ever i can like a little kid. I had a lot of fun as a kid just driving my train around that loop I put on plywood and painted green. So what I like to know is where can I go to learn more about locomotives? Like the names and what they are commonly used for and were.
If you are referring to model trains, and the scale you are interested in is HO (approx 1/8 inch = 1 ft) or N (approx 1/16 inch = 1 ft), then you need Kalmbachs Primer for HO (or N) available at hobby shops or from them online. For other scales, I believe they can also help.
For the “real” railroads, well that is a huge open question. There are tons of books out there, with most geared to a specific railroad or era or area. If you could narrow down your question, then you could hit the library, or Ebay or the local book store.
There is a huge variety of locomotives out there presently and from the past. You might want to start by going to the trains forum dealing with the real railroads. Also there are a number of diesel spotter guide type books out, like this one “Field Guide to Modern Diesel Locomotives” Also you can go to other sites on the web like www.railpictures.net .
Also go to www.wikipedia.org and type in locomotive manufacturers like EMD, GE, ALCO, and MLW.