This document provides an overview of complex event processing (CEP). It discusses how CEP can analyze streams of event data in real-time to detect patterns and infer higher-level events. The document describes different CEP technologies like rule-based, state-based, and query-based approaches. It also outlines requirements for CEP systems like accessing event sources, matching patterns, maintaining state over time, and detecting patterns. Overall, the document introduces the key concepts of CEP and how it can be used to gain insights from real-time event data.