Explanation
The grub-install command is used to install the GRUB boot loader on a device, such as a hard disk or a floppy disk. The command takes one argument, which is the device name where the boot loader should be installed.
The command copies the GRUB files from the /boot/grub directory to the device and writes the boot code to the Master Boot Record (MBR) or the boot sector of the device. The command also creates a device map file in /boot/grub/device.map, which maps the BIOS device names to the Linux device names. The grub-install command is useful for setting up a dual-boot system or for repairing a broken GRUB installation. The command can also take various options to customize the installation, such as --boot-directory, --efi-directory,
--removable, --force-lba, and --no-floppy. References:
* GNU GRUB Manual 2.06: Installing GRUB using grub-install
* grub-install Command Options - The Geek Diary