This dialog box is part of the Language editing modes dialog. These options allow you to specify the names of external utilities (commands or programs) which should be used under various circumstances.
"CRiSP is the only UNIX text editor I've seen that would allow a DOS/Windows
user to be immediately productive. But it also has a seemingly
unlimited list of power-user features. I like it so much at work that I
bought it to use at home (under Linux)."