Social engineering is a new term for some very old ‘con tricks' and is a technique which exploits common, predictable patterns of behaviour in individuals to access secure systems or personal information.
These are techniques which trick you into supplying information for fraud or system access BUT they aren't restricted to the online environment and are just as likely to come to you via a telephone call or even a face-to-face conversation (e.g. a telephone call from someone impersonating a technical support agent, an ‘IT technician' asking you to log on to their machine with your details).
In some instances the smallest piece of personal information can be used to give an air of credibility to these individuals (e.g. a date of birth, details of school attended, workplace) and the increasing popularity of Facebook and the naivety of many users when publishing personal information about themselves, has been a source of information for fraudsters looking for information to gain them a ‘foot in the door'.
Have a look at the 'How to help yourself section' for tips on what to look out for.