A closed-ended question is one that has only a simple, short answer that is usually either "yes" or "no," though there can be more "open" types. The strictest definition is typically a question that has only one answer as either a "true" or "false" condition, such as "Did you like that movie?" or "Is today Monday?" A more "open" form of closed-ended question still only has a single, short answer, but one that is not restricted to just "yes" and "no," such as "How old are you?" or "What day is it?" These are in contrast to true open-ended questions that allow for a wide range of lengthy answers such as "How are you today?" or "What did you think of that movie?"
There are certain advantages and drawbacks to using a closed-ended question. One of the major strengths of these types of questions is that they allow the asker to retain power in the process, since the answer should be brief. They can be used quite effectively to determine very simple types of information and to make data quantitative, or numerical. For example, someone polling about a film might ask "Did you like the movie?" with only "yes" and "no" as answers, allowing a simple analysis comparing the number of "yes" and "no" responses.
One of the major downsides to asking a closed-ended question, however, is that it eliminates a great deal of possible answers, since only one remains viable. For example, in the previous instance, someone may have liked the movie but thought the title was flawed or misleading. Without any ability to provide this type of information, the use of a closed-ended question only determined someone's enjoyment of the film, not if the title would have lead them to see it in the first place. During an interview, this type of question is useful early on, but can prevent a great deal of discovery from occurring in the long run.
Use of an open-ended question helps alleviate many of these weaknesses, though there are certain drawbacks to them as well. Unlike a closed-ended question, open ones have many possible answers and this provides a questioner with much more depth from a response. The information gained from them can be hard to quantify or easily use as part of a numerical study. It is often preferable to have both open- and closed-ended question options as part of a survey or questionnaire; this provides opportunities for both types to be used effectively, allowing each one to diminish the weaknesses of the other.