An Enterprise Service Bus (ESB) is an architecture that integrates different applications by putting a communication bus between them, allowing each application to communicate without dependency on other systems. This decouples systems and moves away from point-to-point integration, which becomes difficult to manage over time. The core concepts of an ESB include using a messaging server as the "bus" to decouple applications, representing data on the bus in a canonical format like XML, and using adapters between applications and the bus to transform data formats and handle tasks like routing and security. When choosing an ESB platform, considerations include lightweight footprint, modular design for customization, and ability to host business logic and publish services rather than just medi