This chapter provides a comprehensive overview of the foundational concepts underpinning blockchain analytics, emphasizing the technological, structural, and operational principles of blockchain systems. It begins by delineating the historical evolution of blockchain technology, from Bitcoin’s inception to the emergence of smart contracts and decentralized applications. Core blockchain features, including decentralization, immutability, and consensus mechanisms, are systematically analyzed to highlight their implications for data transparency and traceability. Furthermore, this chapter explores the architecture of various blockchain layers, the nature of on-chain and off-chain data, and the unique analytical challenges posed by pseudonymity and data complexity. By establishing a clear understanding of these technical fundamentals, this chapter lays the groundwork for advanced analytical approaches in subsequent sections, underscoring the critical role of blockchain analytics in fostering compliance, enhancing security, and enabling data-driven decision-making in decentralized environments.