The Hub-and-Spoke VPN topology is designed to establish a persistent connection between a central hub, typically an organization's main office, and its various branches. This topology is efficient for organizations with many branch offices that need to communicate with the main office but not necessarily with each other directly. It uses a third-party network or the Internet to create these connections, allowing for secure communication over potentially insecure networks like the Internet. The hub-and-spoke model reduces the number of tunnels required compared to other topologies, such as full mesh, which needs a direct tunnel between each site.