Trunking in my words. Where there is a frequency that serves as the control channel and all the radios on the system are connected to it and it is attached to a computer and when someone talks on a talkgroup, the computer sends out a voice channel assignment for the radio to talk on and the other radio(s) and scanners receive the voice on that frequency. I have a Pro 94 and really could not understand the trunking on there but since everything has been rebanded by law, I don't think that scanner will do trunking. It will only do Analog voice on a Motorola 3600 system but will not do a P25 9600 Digital system. Hope this helps!
Looking at the database page for Graves County, it appears that most of the public safety agencies are using digital radios, as designated by the P25 in the Mode column. Your Pro-94 will not handle digital transmissions. McCracken County shows to be on this system. While that trunked system has been rebanded, you might be able to trunk track that system since all of the system frequencies have a numeral 5 in the fourth decimal place. The easier to read manual for the Pro-94 might help. As I don't own that model, my knowledge of it is somewhat limited.