This document is a guide that explains the evolving nature of digital banking and what it means to be a digital bank in today's financial landscape. It outlines the distinctions between various types of banks, including challenger banks, neobanks, and digital banks, emphasizing that a digital bank fundamentally operates differently from traditional banks by leveraging technology to enhance customer experiences. The guide discusses the importance of digitalization, which involves a comprehensive transformation of banking processes driven by technology, rather than merely digitizing existing services. It highlights the necessity for banks to adapt to changing customer expectations and the competitive landscape shaped by fintech innovations. Additionally, the document presents the concept of two-speed architecture, which allows banks to modernize their services while maintaining legacy systems. It concludes by asserting that the future of banking is inherently digital, with all banks expected to embrace digitalization as a standard practice.