What is Redis?
Redis, which stands for Remote Dictionary Server, is a fast, open-source, in-memory key-value data store for use as a database, cache, message broker, and queue.
Key-Value store is a storage system where data is stored in form of key and value pairs. When we say in-memory key-value store, by that we mean that the key-value pairs are stored in primary memory(RAM). So we can say that Redis stored data in RAM in form of key-value pairs.
In Redis, key has to be a string but value can be a string, list, set, sorted set or hash.