think of the yard as your local airport-the yardmaster is in charge of movements, like the tower at an airport. There's ground crew there too, like switchmen, tower men, etc. Hostlers would bring the engines from the 'shop,' to the ramp/gate, where the actual (road) train crew would take over.
once you depart the terminal and are 'on the main,' the dispatcher (ATC/Tracon) is in charge of train spacing, meet locations, etc
Pilot responsibilities are split between the Conductor, and Engineer. Remember, back when cabooses were used, the conductor would usually be located in the caboose, which had a brake valve, which the conductor could use, if he thought the engineer was going to fast, or was being unsafe. The conductor and other train members were also on the lookout for hot boxes, etc, while running
On diesels, fireman is sort of like copilot/flight engineer(pilot in training) keeps eyes out and on some gauges, + trouble shoots engine problems while running
Station agents report progress of train to Dispatcher, called 'OSing,' or 'On (Dispatcher's Train) Sheet,' which is determined by the schedule, assuming there is one, before radios, and such, or modern train detection systems. In the age of CTC, dispatchers transmitted some of their directions to train crews thru signal indications, besides train orders. Depending on what the instructions were, if they were issued as train orders, a crew might have to stop the train and sign for them. Train orders often came in Form 19, or Form 31, one of which could be picked up on the fly, the others needed to be signed for. There were also Form A, which I forget what they were for-maybe where maintenance was going on. Today, Track Warrents are used, mostly or in some cases instead of train orders. Dispatcher reads his instructions to crew, and engineer repeats them verbatim back to the dispatcher. Track warrents are good from point a, to point b, on a certain date, for a certain period of time, which are included in the warrant.
Some trains had a head, and a rear brakeman, or on passenger trains, an assistant trainman, or assistant conductor. It depends some on the period, and rr. Going back further, there were also assistant brakeman, station masters, yardmasters, towermen, etc.
Also, if you wanted to be an engineer, you started out as a fireman. For conductor, you started as a brakeman. Generally, the longer distance runs paid more, than say a local passenger or freight train, and also yard or station switcher engineers. Generally for yard and station masters, you started at a small, remote location, and worked your way up to larger and larger stations/yards, until you worked at the most important station/yard. Everything was based on seniority. Of course, depending on the situation, if you wanted to be home every night, and were in the 'operations department,' you might pass up the long distant assignments for a local, or yard/station job, so you could be home every night, which usually paid less. Sort of like flying the short haul, or commuter/regional airlines. A shortline railroad, was similar to a regional, or commuter airline, as were branch line assignments on the larger systems.
Hope this helps some.
You might look for a book called "Rights of Trains," which explains 'the rules of the road,' in terms of which train(s) have priorities over other trains, in different situations.