The article outlines various methods for tracking user behavior online, primarily through cookies and other identifiers. These tools allow websites and apps to recognize users each time they connect, enabling targeted advertising. For instance, a car manufacturer can tailor ads for electric vehicles to urban users after office hours, while a watercolour paint producer can avoid mismatched content by focusing on audiences interested in art rather than home improvement. It details how advertisers create profiles based on user activity. If someone reads articles on bike accessories, they might receive ads for related products. This profiling combines data from different websites and apps to refine ads to user interests. Advertisers also rely on statistics to understand audience characteristics. For example, an online bookstore might analyze visitor behavior to determine the average demographic of buyers. Retention periods for data vary, with some information stored for up to 730 days, especially for creating and using profiles for personalized advertising. Security measures are also highlighted, including efforts to prevent fraud and fix errors. Overall, the article reveals the complex ecosystem of online advertising and user tracking, emphasizing the balance between targeted marketing and user privacy.