A short question about init.d

Hello list, I have always thought that the stop scripts linked in /etc/init.d/rc<x>.d as "/etc/init.d/rc3.d/S01httpd" are called by init.d when the system enter in the corresponding runlevel ( in example, when system switchs to runlevel 3). Although I have been revising the man documentation about init.d in a Suse 7.3 and I find the next: "....There are two kinds of symbolic link: start links, which are called when entering a run level, and stop links, which are called when leaving a run level......" Does anyone clear up me this subject ?. I think that in Red Hat distributions, the stop scripts in a certain runlevel are called when system enter in that runlevel. Thank you in advantage