HFS+ is the successor of HFS, and was introduced by Apple in Mac OS 8.1. The main reason is support for larger disks than HFS and allowing for more than the rather poor limit of 65 thousand files, but it also has support for journaling and links. The format is described in Apple's "legacy" documentation, as technote 1150.
sectors 0 & 1 are the boot sectors. sector 2 has the volume header