Master Boot Record
MBR is an older way to handle file system. MBR exist since 1983, even before Microsoft Windows exist. MBR contains the information about how the file system be handled. It also holds the bootloader. Optionally it contains 32-bit disk time stamp and signature.
Limitations
MBR has a few limitation, which is the reason why MBR is superseded by GPT (GUID Partition Table). The limitations are:- MBR can only handle maximum hard disk size of 2 TiB (~2.2 TB).
- MBR can only have maximum of 4 primary partition, or 3 primary partition and 1 extended partition. (The extended partition can contains unlimited amount of logical partitions, but logical partition cannot be booted.)
This article is referred from Wikipedia's Master Boot Record article.