Social engineering is the practice of deliberately attempting to effect changes in society. According to the Oxford English Dictionary, the phrase arose with this meaning at the end of the 19th century.
More recently, the phrase social engineering has been used in a very different sense: attempts at gathering information from any social element involved in a social activity (generally a human being), often used in a cybercrime. People using that technique try to exploit a weakness, like in a software or an operating system, to collect valuable information. Human beings are often more vulnerable than computer systems, mainly because of lack of education.
Phishing is a very basic technique of social engineering, where the victim gives credentials to someone that seems to be a trustworthy interlocutor. Another common technique of social engineering is to find answers to security tips, added to ensure some privacy protection especially in many web sites, elsewhere like in a chat session.
The goal of the social attacker can be slandering, phishing, competition, glory, competitive advantage or any motivation.