What are they IST files and What are they use for?

[PhoenixBank]

I have some files but I don’t known how to use

 

[risktaker42069]

.IST are files extentions, but ofcourse you mean about their contect. this file is like a copy of most existing commands of original card, its very important, you can generate it in the x2 software, in the istgen tab.