This document provides an overview of measuring Facebook advertising using Facebook pixels. It discusses how Facebook pixels allow tracking of user behavior between a website and Facebook. The document demonstrates how pixels can detect when a user visits a website and then serve them ads on Facebook. It provides examples of how pixels tagged a user's behavior and showed related ads. Finally, it lists five use cases for pixels that Facebook recommends: driving more conversions, finding a larger audience, measuring page post results, calculating ROI, and remarketing to site visitors.