Oracle Coherence is a data grid that provides reliable, scalable universal data access and management. It manages information in a grid environment where multiple servers work together to store, process, and manage data as a service. Coherence uses different topologies like replicated, partitioned, and near caching to distribute data across servers. It supports features like events, queries, and various caching modes like read-through, write-through, and write-behind caching. Coherence improves performance by reducing latency through locality of data and parallel processing. It increases availability through redundancy and removes single points of failure. Scalability is achieved through scale-out functionality and the ability to add more nodes to the Coherence cluster.