Redis, which stands for REmote DIctionary Server, is an open-source, in-memory data structure store, used as a database, cache, and message broker. Unlike traditional disk-based databases, Redis keeps its primary dataset in RAM, which allows for extremely low latency and high throughput, making it exceptionally fast for read and write operations. While fundamentally a key-value store, its power lies in supporting a variety of complex data structures, such as lists, sets, sorted sets, hashes, and streams, which enables developers to build highly performant, real-time applications for use cases like caching, session management, leaderboards, and message queuing.