A message queue is a communication mechanism used in software systems to facilitate asynchronous message exchange between different services, components, or applications. It decouples the sender and receiver, allowing messages to be transmitted without both systems being online or available simultaneously. Message queues ensure that messages are reliably stored until they are consumed, making them crucial for distributed systems and microservices architecture.

Producers send messages to the queue, and consumers retrieve them when ready. This method allows systems to handle high traffic volumes and process tasks asynchronously, ensuring stability even during peak loads. Popular message queue systems include RabbitMQ, Apache Kafka, and Amazon SQS.

Message queues support fault tolerance by ensuring that messages are not lost in case of service failures, and they improve system resilience by allowing parts of an application to remain functional even when others are overloaded or temporarily down. They are commonly used for tasks like email notifications, background processing, data pipelines, and log aggregation.