Open and closed questions are two types of questions that can be used in a tech support call. The types of questions are used depending on what type of attitude the caller has, and what types of statements they are making.
Open questions are used for a caller who would call up and complain about a problem such as "the internet is not working", or "my computer is messing up". Open questions are used to establish a general technical picture of the customers issues, to make the customer more comfortable with speaking with the technician, and with giving the technician a better understanding of the customers technical ability. Depending on what branch (ISP, hardware, software, etc.) of support is being donem the questions can differ, but they are usually along the lines such as: "has this ever occured before", "how long has this been going on", "has anything changed on your system". These simple questions often can give a technician better hints about what avenues of inquiry to follow.
Closed questions are used with customers that are too talkative, especially when they are talkative about irrelevant issues; or with customers that have a better degree of technical knowledge, and just need to be asked for specific information. Closed questions should be phrased in such a way that the caller can only answer them either with a yes or no answer, or with a piece of data. Technicians should be careful, however, to not fence in customers with such questions until they are truly aware of what problem the customer has. Examples of closed questions would be: "is use area code rules checked or unchecked?" , "has the computer ever been able to auto-detect this piece of plug and play equipment" and "how many modems are listed as installed on your computer".
Judicious use of open and closed questions can easily give a technician the best road to both establishing a rapport with their customer and an understanding of their specific technical problems.