The "Classification Problem" involves data which is divided into two or more groups, or classes. In our example above, the two classes are "switched supplier" and "didn't switch". The data mining software? is asked to tell us which of the groups a new example falls into.
So, we might train the software using customer records from the last year, divided into our two groups. We then ask the software to predict which of our customers we're likely to lose.
Of course, to ensure we can trust the predictions, there is generally a testing or validation stage as well.
See also: Data Mining Software
Backlink: http://www.the-data-mine.com/bin/view/Misc/ClassificationDiscovery