CDR
    In Internet telephony,
        a Call Detail Record is a data record that contains information related to a telephone call,
        such as the origination and destination addresses of the call, the time the call started and
        ended, the duration of the call, the time of day the call was made and any toll charges that
        were added through the network or charges for operator services, among other details of the
        call. 
 
In essence, call accounting is a database application that
            processes call data from your switch (PBX, iPBX, or key system) via a CDR (call detail
            record) or SMDR (station message detail record) port. The call data record details your
            system's incoming and outgoing calls by thresholds, including time of call, duration of
            call, dialing extension, and number dialed. Call data is stored in a PC database.