When I do the chkconfig command like this:
chkconfig --list | grep -i on

I get the following resuts:

clamd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
kudzu 0:off 1:off 2:off 3:on 4:on 5:on 6:off
syslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off
netfs 0:off 1:off 2:off 3:on 4:on 5:on 6:off
network 0:off 1:off 2:on 3:on 4:on 5:on 6:off
random 0:off 1:off 2:on 3:on 4:on 5:on 6:off
rawdevices 0:off 1:off 2:off 3:on 4:on 5:on 6:off
pcmcia 0:off 1:off 2:on 3:on 4:on 5:on 6:off
keytable 0:off 1:on 2:on 3:on 4:on 5:on 6:off
apmd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
gpm 0:off 1:off 2:on 3:on 4:on 5:on 6:off
autofs 0:off 1:off 2:off 3:on 4:on 5:on 6:off
iptables 0:off 1:off 2:on 3:on 4:on 5:on 6:off
isdn 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
portmap 0:off 1:off 2:off 3:on 4:on 5:on 6:off
nfslock 0:off 1:off 2:off 3:on 4:on 5:on 6:off
sendmail 0:off 1:off 2:on 3:on 4:on 5:on 6:off
rhnsd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
crond 0:off 1:off 2:on 3:on 4:on 5:on 6:off
xfs 0:off 1:off 2:on 3:on 4:on 5:on 6:off
xinetd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
cups 0:off 1:off 2:on 3:on 4:on 5:on 6:off

Can someone explain what those numbers mean? Like the 0,1,2,3,4,5 and 6. What those numbers mean?

0-6 are runlevels. Typically for Redhat based distributions:
0 - Halt the system
1 - Single-user mode
2 - Multi-user mode (without networking)
3 - Multi-user mode
5 - Multi-user mode, graphical login
6 - Reboot the system

google for more info.
http://www.justlinux.com/nhf/Booting.../SysVinit.html
http://www.redhat.com/docs/manuals/l...down-sysv.html

Thanks for your quick answer