This lecture covers the legal aspects of personal data processing, focusing on the General Data Protection Regulation (GDPR). It explains the broad scope of personal data, legal bases for processing, data protection rights, and real-life cases. The lecture also delves into the history of web tracking, the same origin policy, and crafty workarounds used by websites to track users. Additionally, it discusses the challenges posed by apps in terms of user privacy and the implications of real-time bidding in the online advertising ecosystem.