Hi Sumon,
DLP Endpoint Discover is for endpoint solution like endpoint server,endpoint agents(discover & prevent) etc.- this will search confidentail data on endpoints only
DLP Discover Plus is for discover and protect component of DLP.- this will search confidentail data on file servers & data repository
please read below
https://www-secure.symantec.com/connect/forums/dlp-license
https://www-secure.symantec.com/connect/forums/symantec-dlp-licensing
https://www-secure.symantec.com/connect/forums/vontu-dlp-endpoint-agent-behavior-if-license-exceeded