Cloud Pub/Sub is a messaging service provided by Google Cloud that allows applications to communicate with each other in real-time. It uses a publish-subscribe model, where messages are sent by publishers and received by subscribers. This decouples the components of an application, enabling them to scale independently and improving overall system reliability. With Cloud Pub/Sub, developers can easily send and receive messages across different services and platforms. It supports various programming languages and can handle large volumes of messages, making it suitable for applications like data processing, event-driven architectures, and real-time analytics.