The StackExchange sites are a collection of websites on various topics where people can ask questions and get answers from members of that community. People can also up-vote or down-vote both the questions and the answers, as well as add comments regarding either. People receive ranking points, called ‘reputation’, for asking questions and on how many up-votes/down-votes their questions and answers receive. It’s intended to drive an active (and interactive) community of people around each subject area. The first and most popular of the sites is StackOverflow.