Redis (Remote Dictionary Server) is an open-source, in-memory data store used as a database, cache, and message broker. It offers lightning-fast data retrieval by storing data in memory, making it ideal for real-time applications like gaming, analytics, and chat systems. Redis supports data structures such as strings, hashes, and sets, providing versatility for different use cases. Its features include persistence options, pub/sub messaging, and clustering for scalability. Redis is widely used to improve application performance and scalability.