Social engineering, in the context of security, is understood to mean the art of manipulating people into performing actions or divulging confidential information.While it is similar to a confidence trick or simple fraud, it is typically trickery or deception for the purpose of information gathering, fraud, or computer system access; in most cases the attacker never comes face-to-face with the victims.
The Social-Engineer Toolkit (SET) is specifically designed to perform advanced attacks against the human element. in this type of attack human behaviour is exploited. i found some of the best video demo of this tool.
have a look on this. http://www.google.com