WebSphere MQ is a messaging middleware developed by IBM that enables different applications to communicate with each other by sending messages. It allows for reliable and secure message delivery between systems, regardless of their location or platform. This makes it easier for businesses to integrate various applications and services, ensuring that data flows smoothly across different environments. The primary function of WebSphere MQ is to facilitate asynchronous communication, meaning that the sender and receiver do not need to be active at the same time. This capability helps improve system performance and reliability, as messages can be queued and processed when the receiving application is ready.