Google Analytics is a free tool that allows publishers to measure website traffic, conversions, and visitor behavior. It provides insights into how visitors arrive on the site and what actions they take through metrics related to acquisition, behavior, content, social media, mobile usage, and conversions. The presentation emphasized using ABC metrics in Google Analytics - acquisition, activation, retention, referral, and revenue - to understand website performance and drive actionable insights. Case studies were provided on how one publisher leveraged different Google Analytics metrics and reports to improve their marketing strategies and content over time.