Central banks around the world are exploring the idea of creating digital currencies for retail and wholesale payments. Different models for these digital currencies have been studied, with some focusing on simplicity and independence from financial intermediaries, while others prioritize speed and reliability in processing transactions. Retail digital currencies aim to provide users with a secure and widely accepted form of payment, while wholesale digital currencies offer faster and cheaper cross-border payments. Projects in China, Sweden, Canada, and Singapore have shown promise in developing these digital currency systems.