chkconfig vs. /etc/rc.d/init.d/httpd -- what does each do best?

[Mark Berkwitt]

/etc/rc.d/init.d/httpd  seems to work well for me.  I can start, stop or find 
the status of apache at will.  I just can't set apache to start at boot.

I ran 
# /sbin/chkconfig --add httpd
then
# /sbin/chkconfig --list httpd
httpd	0:off	1:off	2:off	3:off	4:off	5:off	6:off

What is this, and what function does it provide.

What is chkconfig for and why should I use it?