Redis is often called a "data structure server." What does that mean?

Unlike key-value stores that only support binary blobs as values, Redis values are typed data structures — lists, hashes, sets, sorted sets, bitmaps, streams, and more. Each type comes with native atomic operations (e.g., LPUSH, ZADD, PFADD) that execute on the server side, eliminating round-trips. The data structure lives in the server, not just in your application.