A privilege log is a document that describes documents or other items withheld from production in a civil lawsuit under claims of attorney-client privilege

Attorney-client privilege

Attorney–client privilege is a legal concept that protects certain communications between a client and his or her attorney and keeps those communications confidential....

, work product doctrine

Work product doctrine

In American civil procedure, the work-product doctrine protects materials prepared in anticipation of litigation from discovery by opposing counsel...

, or trade secrets.

Generally, it is the withholding party's burden to provide sufficient information on its privilege log to allow the opposing party or court to test the claim of privilege.