What Is "Social Engineering"?

Actually I did not know what Social Engineering really means in the term of computer science. Therefore, I researched on the Internet, and according to e-Words, it is to obtain the important information like passwords by “Social” ways such as conning or eavesdropping from users or owners of the network. For example, a person watches the keyboard when someone is typing a password behind him or her, or a person searches for something related to important, individual information in the garbage of the office, or a person, who pretends as an owner, calls or sends e-mails to users and get the significant information, saying “you need to re-input your password because we will change our service into new one. ” I felt scary through reading the article.