In this course we’re going to take a look at Redis. Redis isn’t exactly a database: it’s not relational or document-oriented. Instead, it’s a key-value store—every “record” is just label and a piece of data. That might sound boring, but I think you’ll find that Redis has a lot to offer.
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.
Redis is used by many large websites to inplement caching on their backend.