Recommender systems include processes that are conducted largely by hand, such as manually creating cross-sell lists, and actions
that are performed largely by computer, such as collaborative filtering. We will refer to the latter as automatic recommender
systems. Automatic recommender systems are specialized data mining systems that have been optimized for interaction with
consumers rather than marketers. They have been explicitly designed to take advantage of the real-time personalization
opportunities of interactive e-commerce. Accordingly, the algorithms focus more on real-time and just-in-time learning than on
model-building and execution. We study both manual and automatic recommender systems since each offers many interesting ideas
about the presentation of recommendations to consumers. This paper serves as an introduction to the elements of recommender
systems and their application to e-commerce.