PNR means Passenger Name Record. It is basically a travel record of a single individual or group of individuals that is stored in Railway computerized reservation system. It is a ten digit number written on the top left corner of rail ticket provided to a person whenever he goes for rail ticketing for a train journey. This PNR number presents the current status of a passenger's reservation. By using reservation status device a passenger can find out the - confirmed, waiting or in RAC status.
http://www.irctcpnrstatusinfo.com/