As its name indicates, algorithmic regulation relies on the automation of regulatory processes through algorithms. Examining the impact of algorithmic regulation on the rule of law hence first requires an understanding of how algorithms work. In this chapter, I therefore start by focusing on the technical aspects of algorithmic systems (Section 2.1), and complement this discussion with an overview of their societal impact, emphasising their societal embeddedness and the consequences thereof (Section 2.2). Next, I examine how and why public authorities rely on algorithmic systems to inform and take administrative acts, with special attention to the historical adoption of such systems, and their impact on the role of discretion (Section 2.3). Finally, I draw some conclusions for subsequent chapters (Section 2.4).