http://en.wikipedia.org/wiki/Non-disclosure_agreement
Non-Disclosure Agreement
A non-disclosure agreement (NDA) (often known outside of the United States as a confidentiality agreement; occasionally called a confidential disclosure agreement or CDA, or secrecy agreement), is a legal contract between at least two parties that outlines confidential materials or knowledge the parties wish to share with one another for certain purposes, but wish to restrict access to. It is a contract through which the parties agree not to disclose information covered by the agreement. An NDA creates a confidential relationship between the parties to protect any type of confidential and proprietary information or a trade secret. As such, an NDA protects non-public business information.
NDAs are commonly signed when two companies or individuals are considering doing business and need to understand the processes used in each others business for the purpose of evaluating the potential business relationship. NDAs can be "mutual", meaning both parties are restricted in their use of the materials provided, or they can restrict the use of material by a single party.
It is also possible for an employee to sign an NDA or NDA-like agreement with an employer. In fact, some employment agreements will include a clause restricting employees use and dissemination of company-owned "confidential information." NDAs are used in the IT field, and are often given directly prior to taking a certification exam.
In rare cases, the contract may state that the existence of the NDA itself cannot be disclosed.
