The Unix filesystem is structured differently than a PC or a MacIntosh. All disks, EIDE or SCSI use a Master Boot Record, which always where the drive can locate it, and contains code to bootstrap the disk so that the operating system can be found in the Boot Sector.
Sun Sparc systems running Solaris Unix have a "Volume Table of Contents" (VToC) in the boot sector which contains a list of files and directories in a linked, tree-like structure. This is not physically how it's laid out, but if you were to imagine it as a 'logical' representation, the Unix Filesystem uses pointers and indirection to address areas of the disk.
The VToC contains lists of filenames. For the purpose of this discussion, there is no difference between a directory, a device driver and an ordinary file. They are all just names to the VToC. These names "point" to what is called an "information node" (inode). The inode contains information about the file itself, such as size and permissions for the user, group and others, as well as access list information.
The inode points to sets of 8kb data blocks on the disk. Within these blocks can either be actual file data, or other information.