What is exactly "Arch Fallback" in the Arch boot menu?
The Arch Wiki mkinitcpio page explains the difference between the two:
The fallback image utilizes the same configuration file as the default image, except the autodetect hook is skipped during creation, thus including a full range of modules. The autodetect hook detects required modules and tailors the image for specific hardware, shrinking the initramfs.
You can create your own image by using the
From this post in the Arch Linux forum (edited for readability):
So (as noted in a comment) it's an initramfs that loads everything. The kernel is the same.