I always think of the gold rush in the 19th century when I think of data mining. Just as these miners were looking to strike it rich in gold, data miners are hoping to strike it rich in insights. Data miners are trying to find that "golden nugget" of data or information that will help boost their business profits or take them from a struggling start up to a million or billion dollar going concern.
Data mining has been around for a long time but with the improvements in computing power and in the era of big data, it is a key component within data science. It is also used interchangeably with the term Knowledge Discovery. There are really two big areas that data mining focuses on: descriptive modeling and predictive modeling.