inetd/xinetd/standalone

I found the following statement at ISPconfig.org, and am not sure I understand what I'm being told: They say that the ISPconfig service supports "vsftpd as inetd/xinetd/standalone version". I assume "standalone" means, "launched manually" and not as part of the bootup sequence, or something like that? Are not inetd and xinetd just ways to configure services to run? How are they different than the runlevel schemes with script in /etc/inet.d? Peter