Redis is an open-source, in-memory data structure store commonly used as a database, cache, and message broker. It supports various data types like strings, hashes, lists, sets, and more, providing high performance for real-time applications. Redis is known for its simplicity, speed, and versatility in handling large volumes of data. It also offers features like persistence, replication, and high availability for mission-critical systems. Redis is often deployed in environments that require low-latency data access and scalability.