Mule is an open-source enterprise service bus and integration platform that allows for integration across systems and protocols. It uses a graphical development environment called Anypoint Studio and provides tools for management and security. Mule supports common transports and messaging protocols like AMQP, JMS, and WebSphere MQ to connect applications and data sources. The Universal Message Object defines the parameters for internal messaging between components to set and get variables based on user needs and program functionality.