Pub/Sub is a messaging pattern that allows different systems or components to communicate with each other asynchronously. In this model, a publisher sends messages to a topic without needing to know who will receive them. Subscribers can then listen to that topic and receive messages whenever they are published, enabling a decoupled architecture. This approach is commonly used in cloud services, such as Google Cloud Pub/Sub, to facilitate real-time data processing and event-driven applications. It helps improve scalability and reliability, as publishers and subscribers can operate independently, allowing for easier maintenance and updates.