The boot sector is a dedicated section of a hard disk or other storage device that contains data used to boot a computer system. It includes the master boot record (MBR), which is accessed during the boot sequence.
The boot sector is typically located at the very beginning of a disk, before the first partition. It includes the partition map, which identifies all the partitions on the disk. It also defines which partition contains the startup data (such as the operating system). This lets the computer know which partition to access when starting up. Therefore, if a disk's boot sector becomes corrupted or contains invalid data, the computer may not be able to start up from the disk. If this happens, you should run a disk utility or antivirus program to try and fix the problem.