If you don't know what it is, don't wrry about it.
Trunking is esentia)y channels with more precise frequencues ...I 600.0006 versus 600.06. It allows for more radio channels. Some radios are not sensitive enough to pick up these subtle differences, like the BC75XLT. The BC125AT can. It has "analog trunking"
Digital versus analog is a whole other beast that I won't go into detail here. It essentially allows for clearer traffic and the abikity to encrypt radio messages so Jon Q. Public cant listen in, mainly for Law Enforcement. It is extremedy expensive to upgrade a system from analog to digital and I don't see railroads doing it any time soon.
Analog radon will work just fine for the time being.