The new Recommendation Module for Drupal is a "collaborative filtering" engine. This means that the module predicts interesting nodes, according to your personal tastes.
The innovative principle is based on "automated user-based collaborative filtering". Check, for example, Amazon.com's "Customers who bought this book also..." or the MovieLens university research project.
Think of it as a "word-of-mouth" system, where friends would recommend you interesting nodes.