A message queue is a communication method used in software systems to allow different parts of an application to send and receive messages asynchronously. This means that one part of the system can send a message to the queue without waiting for the other part to process it. This helps improve efficiency and ensures that messages are not lost, even if the receiving part is busy or temporarily unavailable. In a typical setup, a producer sends messages to the queue, while a consumer retrieves and processes them. This decouples the components, allowing them to operate independently. Popular implementations of message queues include RabbitMQ, Apache Kafka, and Amazon SQS.