I was once like you and I still am to some degree.
In my area, the "ROAD" channel is for calling the dispatcher and communicating with other trains using the line. They use base and mobile simplex and NOT repeaters where I live. There are several radio towers along the line, all tuned to the same frequency. 1212 is the channel, which means the locomotive radio transmits and receives on channel 12 (160.29 MHz.) There is a tower for each portion of a track. These towers constantly monitor the channel for a DTMF (telephone digits) tone sequence. When it hears that correct tone sequence, it activates the telephone at the dispatchers office and also repeats and audiable tone back to the engineer and conductor. Tower 1 might have the tone sequence 741; tower 2 might have 742, etc. To call the dispatcher, the conductor keys up their radio, dials the tone to the corresponding tower and is connected to the dispatcher. Sometimes the dispatcher answers immediately if he/she isn't busy. I would imagine something flashes on a computer screen at the dispatcher's console indicating which tower received the call.
He/she would connect to that aforementioned radio tower and say "Dispatcher answering tower 1"
Now, since this is a simplex system, you might only be able to hear the dispatcher (since the radio towers have better antennas and put out more power.) Sometimes you will also be able to hear the train crew (if you are close to to a passing or parked train.)
Now there are three types of traffic control, which are verbal instructions that the dispatcher gives the train and crew for which tracks to occupy.
The form I am most familiar with (and used on my local line) is Track Warrant Control. To be able to understand the conversation, you will need to know the mile posts, sidings, junction and towns along the line. Direct traffic control is similar and simpler, but not as flexible.
A track warrant instruction would sound like:
Warrant number 827 (my district number) dash xx, the individual warrant number.
x in box 2 (when box two is exxed or marked or checked, it means proceed from point a to point b.) this is probably the most common instruction on a warrant.
Look up track warrants on wikipedia
Track warrant - Wikipedia, the free encyclopedia
that link will give detail on the meaning of each box number on a warrant.
the train crew will repeat that warrant back to the dispatcher and it will go into effect as soon as the dispatcher ok's it, along with the time it is oked.
If you have any additional questions, I will be happy to give you more information.