RabbitMQ is an open-source message broker that facilitates communication between different applications or services. It allows messages to be sent and received in a reliable manner, ensuring that data is transmitted even if one part of the system is temporarily unavailable. This makes it particularly useful in distributed systems where various components need to work together seamlessly. The core of RabbitMQ is based on the Advanced Message Queuing Protocol (AMQP), which defines how messages are sent and received. It supports multiple messaging patterns, such as point-to-point and publish/subscribe, making it versatile for various use cases in software development and cloud computing.