This dialog is a part of the "Advanced SFX options" dialog and allows to choose a self-extracting module. Note that not all modules support advanced SFX options. They are supported by GUI RAR and ZIP modules (Default.SFX and Zip.SFX), but not by console RAR module (WinCon.SFX) and DOS RAR SFX module (Dos.SFX).
See also: