PNR stands for passenger name record. It is 10 digit number on IRCTC train ticket and generally printed on left side top corner of Indian Railway counter ticket. It is record of passenger's jouney details such as train name, number, date of journey, class of travel (SL, AC, EC, GN, SS), pasenger booking details & charting status stored on Indian railways database. Every time user books a ticket on IRCTC website or Indian Railway ticket counter a new PNR is generated and get flushed after journey ends.
Procedure to check IRCTC PNR Status
Procedure to check IRCTC PNR Status using SMS service