An enterprise service bus (ESB) implements a communication system between mutually interacting software applications in a service-oriented architecture (SOA). It implements a software architecture as depicted in the picture.
Mule is the most used open source integration platform. MuleESB’s low cost along with easy configuration, expansion, and flexibility make it very popular. Java developers will find MuleESB easy to work with because it is Java centric. There’s also a powerful set of XML schemas in MuleESB. The creation of integration flows is very straightforward. MuleESB can have fairly complex integration flows up and running in minutes. It has many connectivity, routing, and transformation options right out of the box.
Anypoint Platform (former Mule ESB): Open Source Integration Platform
Anypoint Platform (formerly known as Mule ESB) is the most-used integration platform for the connection to any application, data source or programming interface, whether in the cloud or on-premise. With the Anypoint Platform™, MuleSoft provides a complete integration platform, which is based on reliable Open Source technology, thus eliminating costs and effort required for a point-to-point integration.