Walmart tracks the habits of the 100 million customers who visit it stores each week and responds with products and services directed toward those customers' needs based on the information collected. This is an example of marketing.

database

Explanation: By tracking the habits of the 100 million customers who visit it stores each week and by responding with products and services directed toward those customers' needs based on the information collected, Walmart is engaged in database marketing.

A database is simply a collection of (usually) organised information in a regular structure, usually but not necessarily in a machine-readable format accessible by a computer. The details of customers both previous and potential, contained in a database can be used in direct marketing to generate personalized communications for promoting a product or service for marketing purposes. As such, the practice leverages customer data to deliver more personalized, relevant and effective marketing messages to customers making marketing communications more targeted, efficient, personalized, and an opportunity to improve customer service and experience.