In the Unix style rc directory structure we have /etc/rc.d directory which have a few rc scripts for each run level(which are also called init scripts). All programs started or stopped on that level are listed in those scripts. You don't have different scripts to start, stop and restart these applications.
In the System V rc directory style we have the following dirs:
/etc/init.d/
/etc/rc.d/rc0.d/
/etc/rc.d/rc1.d/
/etc/rc.d/rc2.d/
/etc/rc.d/rc3.d/
/etc/rc.d/rc4.d/
/etc/rc.d/rc5.d/
/etc/rc.d/rc6.d/
or:
/etc/init.d/
/etc/rc.d/
/etc/rc0.d/
/etc/rc1.d/
/etc/rc2.d/
/etc/rc3.d/
/etc/rc4.d/
/etc/rc5.d/
/etc/rc6.d/
In both System V structures we have one script /etc/rc.d/rc which is called with the corresponding runlevel. The rc script then lists all the links found the rcX.d dirs and starts/stops all applications.
The links in the rcX.d directories are links to files in /etc/init.d.
The files in /etc/init.d are called init scripts, which basicly give you the ability to start, stop and restart the corresponding application.
The difference between Unix style init structure and System V is that System V gives you more flexability and it is easyer to manage. But System V introduces more complex software which makes it prone to more bugs and harder to debug.