Rabbit MQ is a Message Broker based around a Queue architecture. Unlike other brokers RabbitMQ ensures FIFO which can be especially critical for background service management unless Sharding is implemented.
RabbitMQ uses AMQP which allows for both PubSub and server client architectures compared to MQTT based brokers.
RabbitMQ does however have non-negligible overheads meaning it is less used in low latency and high frequency applications.