Master Boot Record (MBR) is a type of boot loader that tells a system how the partitions on a disk are organized. Although MBR has been superseded by GUID Partition Table in recent years, MBR is still very prevalent across many systems. Without a boot loader, your system will have a hard time booting into your operating system - whichever Linux distro that may be.
This is a companion discussion topic for the original entry at https://linuxconfig.org/linux-backup-restore-destroy-and-install-mbr-master-boot-record