Software updates are deployed to client computers using the Deploy Software Updates Wizard, much like it is in SMS 2003, but new objects have been introduced and there have been changes to the deployment process. The following document briefly describe these changes.

You can also refer the following link http://blogs.technet.com/configurationmgr/archive/2009/08/17/guide-to-software-updates-deployment-in-configuration-manager-2007.aspx