Can anyone explain Redis Sorted Sets?

Hey folks, I've been playing around with Redis for caching and keep seeing mentions of Sorted Sets. I understand the whole unique elements thing with sets, but the 'sorted' part, and how people actually use it in system design stuff, is a little confusing. Is it really just for leaderboards, or am I missing other common caching or system design applications for them? I'd love to hear what you all think and see some examples!