RabbitMQ is a message queuing software called a queuing manager. Simply put, this is software where queues can be defined, applications can connect to the queue and send a message to it. The message may contain all kinds of information (for example information about a process / task that should be started on another application). The message is stored until the application that is to receive the message connects and is then taken from the queue. The application that received the message then processes it appropriately.