Figure 12.1 shows that the physical disk is divided up into partitions:
Figure 12.1 Partitions
Figure 12.2 shows an idealized Unix file system on a particular partition. HFS+ is actually implemented differently, but this mental model will help you understand the upcoming system calls.
Figure 12.2 Filesystem
The superblock is a block in a known location that has pointers to the rest of the on-disk data structures. Frequently there are redundant copies of the superblock in case the primary superblock gets destroyed.
An inode, ...