In shell scripting, MBR stands for Master Boot Record. It is a small but crucial data structure located in the first sector of a storage device, such as a hard drive. MBR contains information about the disk's partitioning and the bootloader. It's useful for users because it enables the system to boot, manage partitions, and load the operating system. Understanding and managing the MBR is essential for tasks like disk maintenance, repair, and dual-boot setups.