There are a few important BIOSconfig notes on devices:
Floppy means whatever the BIOS considers a removable device. For example, this could be a USB flash drive.
A USB flash drive bigger than 512 MB defaults to being a disk.
A USB/CD-ROM is classed as a CD and not a removable device.
PXE means a bootable network device. For example, an Ethernet controller, or an InfiniBand interface that has booting support in its expansion ROM.
See also What Changes the Boot List