What is "Social Engineering"?

Social Engineering is to steel important information from other people (user, manager) by listening slyly, finding memo that is written password or something important, looking at computer silently, and smooth talking, and so on. Some hackers use telephone. They pretend to be users, call managers, and then ask to change password to new one, but hackers don’t seem suspicious, because they pretend to be friendly. They don’t do technical things like using computer virus, hacking, etc. It is called also Social Hacking and Social Cracking. It is because of incomplete identification. I did not know this word “Social Engineering”. I thought it was kind of works because Engineer sounds like worker about technology. When I was a junior high school student, a man called me and said “This call is about yahoo BB. Now you can try it free. I want you to proceed, so tell me your address, please.” I surely sent a mail to apply, but I felt distrust that he asked me my address on call. Was it hacking????