There's a great episode of Seinfeld where George Costanza decides to do the opposite of what his instincts tell him to do. By the end of the episode, he's met a beautiful woman and landed his dream job with the New York Yankees.
Some investors seek Costanza-esque results by doing the opposite of most other market investors. A contrarian investor looks for opportunities where the popularity of an investment choice in the broader market has led people to drastically misprice certain securities. That means when everyone else is buying a certain stock, the contrarian is selling. When everyone's selling out of a certain industry, the contrarian is picking up shares on the cheap.