What is Attorney-client Privilege?

Legal Definition
Attorney–client privilege or lawyer–client privilege is a "client's right privilege to refuse to disclose and to prevent any other person from disclosing confidential communications between the client and the attorney."

The attorney–client privilege is one of the oldest recognized privileges for confidential communications. The United States Supreme Court has stated that by assuring confidentiality, the privilege encourages clients to make "full and frank" disclosures to their attorneys, who are then better able to provide candid advice and effective representation.
-- Wikipedia
Legal Definition
A legal privilege that works to keep communications between an attorney and his or her client secret. The privilege is asserted in the face of a legal demand for the communications, such as a discovery request or a demand that the lawyer testify under oath. Contrast with attorney's duty of confidentiality.
Illustrative case law
See, e.g. Mohawk Industries, Inc. v. Carpenter, 130 S.Ct. 599 (2009).
See also
Legal Definition
This term applies to the right an individual has for the information he gives his attorney that it be kept confidential.
Legal Definition
Protection of the information that is exchanged between client and lawyer. The honesty is needed for the best representation. Should the bill not be paid the information is no longer priviledged.