Redis and Memcached are both open-source, in-memory key-value data structures stores that are commonly used for caching, but Redis has additional features like persistence, data structures, and pub/sub capabilities that make it more flexible than the simpler Memcached. Real-world use cases for Redis include caching page fragments to speed up websites by 5x, job queuing with persistence and multi-queue/worker support, and caching model predictions to speed up machine learning workflows by 100x.