Social Engineering is a technique used to obtain or attempt to obtain secure information by tricking an individual into revealing the information.
Social engineering is normally quite successful, because most targets (or victims) want to trust people and provide as much help as possible.
Victims of social engineering typically have no idea they have been conned out of useful information or have been tricked into performing a particular task.
The easiest way to breach a security is to obtain credentials and the easiest way to get information is to ask someone for it.
The basic goal of social engineering is to gain unauthorized access to systems or information in order to commit fraud, network intrusion, industrial espionage, identity theft, or simply to disrupt and compromise computer systems.