Volume Boot Record
A Volume Boot Record (VBR) is the first sector of a partition (unlike MBR which is the first sector of a hard disk). A VBR (just like a MBR) also contains some code and data, but it's far less standard. Instead of a Partition Table it usually holds some file system information, like the BIOS Parameter Block (although it's not needed nowadays, many OS's have kept it for compatibility). The code is always OS specific, but in common all versions function the same: locate the kernel on the partition, load and execute it. A really good example of a VBR is the original DOS bootsector, which knew FAT and loaded IO.SYS and MSDOS.SYS from the root directory.
This is file system specific, but the usual is a JMP followed by FS info.