Whenever a new service (like Samba or NFS) is added to a Linux system, it is not configured to start automatically when the system starts up. So, by default, whenever you add a new service, you’ll have to start it manually after the system reboots. ‘chkconfig’ command allows you to configure that newly added service to start after every system start up automatically. Not only this, you can change the configuration so as to add any service at different run-levels. With ‘chkconfig’ you can display the list of services those are configured for startup at a particular run-level.

Full article here:
Tutorial on “chkconfig” Command in Linux with Examples (Your Own Linux..!)