E-Commerce firms very well understand that data is a wealth. The data can provide very crucial and meaningful insights, if used properly. Data Mining is one such way. It is a field of computer science that discovers the patterns in large data sets. This is done using the methods of Artificial Intelligence, Machine Learning, Statistics and Database Systems. Algorithms are made to act on the data set. This often reveals "game changing" results for the industry. Data Mining can be either done manually or can be automated. E-Commerce Firms use this to get to know more about customer's emotions, preferences, and other factors that impact their purchasing style. So they excel in offering a personalized experience through this. It doesn't stay limited to customers. Data Mining is done to keep an eye on the competitors. Read more about it in the article written by Arie Shpanya (contributor to Econsultancy)  at: https://econsultancy.com/blog/67360-why-data-mining-is-the-future-of-online-retailing/