The actual game files, hidden in a format called XDVDFS that Windows and macOS cannot read natively.
However, the original Xbox was unique. While it used DVDs, the Xbox filesystem was proprietary. A standard DVD ISO created by a computer often lacks the specific file structure and security headers that the Xbox BIOS (MCPX) expects to see. This is where the confusion sets in.
While xemu currently focuses on disc images, the development landscape is always shifting. Some users prefer the "Folder" method—where you simply have the game files in a directory on your PC and load the default.xbe directly.
A standard "Redump" ISO includes both partitions. Because the emulator lacks the code to "skip" the video partition automatically, you must convert the file into an XISO first. How to Convert ISO to XISO