VBR may refer to any of the following:
1. When referring to audio, Variable Bit Rate or VBR is a form of encoding an MP3 file by how much data the MP3 file contains.
2. When referring to a network Variable Bit Rate or VBR is a network setup that is capable of handling fixed timing and non-fixed timing traffic.
3. Alternatively referred to as the Volume Boot Sector, VBR is short for Volume Boot Record. It is the first section of each partition on a hard drive that contains information such as the type and size of the partition.
In the above image, is an example of a partitioned hard drive with two partitions. Each partition has a VBR in front of them that contain information about that partition.