The impromptu interview
This kind of interview happens more by accident than anything else. An employer looking to fill a vacant position happens to meet someone that they would consider employing. They then seize the initiative to begin discussing their role with this unsuspecting candidate. Their manner and style of questioning would be a subdued and superficially of a social nature. Very rarely will a job offer ensue from such an encounter. A formal invitation to attend a more official interview could easily ensue from such an exchange of information. Such an interview is likely to occur at a venue of mutual interest such as a job fair, wholesaler's outlet, industry convention, mutual client or a similar setting. That doesn't hurt to be always prepared to sell yourself under any kind of the interview situation no matter how unexpected.