MBR

Master Boot Record (MBR) will be created when you create the first partition on the hard disk. It is very important data structure on the disk. The Master Boot Record contains the Partition Table for the disk and a small amount of executable code for the boot start. The location is always the first sector on the disk.

The first 446 (0x1BE) bytes are MBR itself, the next 64 bytes are the Partition Table, the last two bytes in the sector are a signature word for the sector and are always 0x55AA.

For our disk layout we have MBR:

Notice the first line, we know that the exact location of the MBR is at cylinder 0, head 0 and sector 1.

MBR is the first sector of the computer hard disk drive that tells the computer how to load the operating system, how the hard drive is partitioned, and how to load the operating system

 

In the above picture, is an example of what a partitioned hard disk drive may look like. In this case, the MBR is the first section of the hard disk drive the computer looks at after the BIOS hands control to the first bootable drive. Unlike the VBR, there is always only going to be a maximum of one MBR on a partitioned hard drive.
The MBR is also susceptible to boot sector viruses that can corrupt or remove the MBR, which can leave the hard drive unusable and prevent the computer from booting up.