RVM or Ruby Version Manager allows you to install and manage Ruby environments. Similar tools are Rbenv and chruby. I previously wrote about installing these on a Mac here.
Redis Cache Store is a new feature on Rails 5.2 although support for caching in Rails has been around for some time. A few cache stores already exist like MemCacheStore, FileStore, and MemoryStore. You can also use a custom store so no doubt some people are already using Redis as a cache store.