Redis is an open-source, in-memory data structure store used as a database, cache, message broker, and streaming engine. Redis provides data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs, geospatial indexes, and streams.

Redis is a powerful tool that can be used for a variety of applications. Its in-memory data store makes it a good choice for applications that require high performance and scalability.