DELL NBD Prosupport cover parts ?

Hi friends... 
 Can someone please explain what NBD Prosupport covers ? In dell official website, I found below warranty details for my server, 

Service                    Start date (GMT time zone)            End date (GMT time zone)

Parts Only                   November 12, 2014                          November 12, 2015
NBD ProSupport         November 12, 2014                          November 12, 2019

In this case NBD prosupport will not cover if any hardware has become faulty ? Then what this Next business day prosupport means ? What are all it covers...? 
Please brief... Thanks