The /etc/sysctl.conf file is read in when the system goes into multi-user mode to set default settings for the kernel

The file loader.conf contains descriptive information on bootstrapping the system. Through it you can specify the kernel to be booted, paramet ers to be passed to it, and additional modules to be loaded; and generally set all variables described in loader(8).

The file rc.conf contains descriptive information about the local host name, configuration details for any potential network interfaces and which services should be started up at system initial boot time. In new nstallations, the rc.conf file is generally initialized by the system installation utility.

The purpose of rc.conf is not to run commands or perform system startup actions directly. Instead, it is included by the various generic startup scripts in /etc which conditionalize the internal actions according to the settings found there.