Strong consistency refers to a consistency model in which all read operations receive the most recent write or an error. In other words, data consistency is guaranteed at all times, and every read operation will return the same data. In a system with strong consistency, all nodes have the same view of the data, and any update to the data is immediately propagated to all nodes in the system. This model is often used in systems where data consistency is critical, such as financial systems or online transaction processing (OLTP) systems. However, strong consistency can come at the cost of performance and availability, as it may require increased coordination and communication between nodes to maintain data consistency.