What is the name given to the very first sector of a partition?

The very first sector of a partition is referred to as the Volume Boot Record (VBR). This sector contains important information about the filesystem of that particular partition and is critical for the system's ability to locate and load files. The VBR is responsible for initializing the filesystem on that partition and provides the necessary directives to the operating system on how to read and execute files stored within that partition.

In contrast, the Master Boot Record (MBR) is located at the very beginning of the disk and contains partition information and bootstrapping code for the system to begin the boot process. Physical sector 0 is a more generic term that can refer to the first sector of the disk as a whole and does not specifically denote partitioning. An active primary partition is a designation given to a partition that the system is configured to boot from, but it does not directly refer to the specific sector. Therefore, identifying the Volume Boot Record as the first sector of a partition aligns perfectly with its definition and role within a filesystem.