IST vs CT files, and how to select

[RED-HOT]

I have a list of IST files, but some end in CT, what's the difference?
Also, for some BINs I have multiple IST and CT files, how do you select which one to use for a given Dumps?
Lastly, how do you go about buying lists of more ISTs? Half the Dumps on the autoshops have BINs that aren't in my lists.
Thanks in advance!