What is a CDR (Call detail record)?

A call detail record (CDR) is an information record that is produced by telecommunications equipment that documents the details of a telecommunications transaction such as messages that pass through that device. The record contains different qualities of the call, like time, duration, completion status, source number, and destination number.
A CDR gives metadata - information about information, on how a particular cell phone number and/or user is using the telephone framework. CDRs can also incorporate SMS messaging metadata and any other official communications transmission.