On libreboot.org these instructions can be found:
QEMU
Libreboot comes with ROM images built for QEMU, by default:
Examples of how to use libreboot ROM images in QEMU:
$ qemu-system-i386 -M q35 -m 512 -bios qemu_q35_ich9_keymap_mode.rom
$ qemu-system-i386 -M pc -m 512 -bios qemu_i440fx_piix4_keymap_mode.rom
You can optionally specify the -serial stdio argument, so that QEMU will
emulate a serial terminal on the standard input/output (most likely your
terminal emulator or TTY).
Other arguments are available for QEMU. The manual will contain more
information.
Can somebody translate this? What exactly does it mean?