Data mining… Every day we hear this word on the radio or read about it while having a cup of tea in the morning but not everyone knows exactly what data mining is. The term was first used in 1968, then it was coined by Gregory Piatetsky-Shapiro in the late 80s. Here we must notice the term still has no Russian equivalent. The most popular modern source Wikipedia defines data mining as the computing process of discovering patterns in large data sets involving methods at the intersection of artificial intelligence, machine learning, statistics, and database systems. Meriam-Webster dictionary defines the term as the practice of searching through large amounts of computerized data to find useful patterns or trends. From practical point of view data mining is the process of summarizing data into useful information. That information should help businessmen to increase revenues, cut costs and at the end gain more profit. The conclusions of the experts of the McKinsey Global Institute prove this idea: they estimate that data mining can increase profits in the retail sector by staggering 60% . But to make it possible the companies must use advanced statistical tools and expert system.