Curating means taking the time to know if a post is worth something. Curators usually are also trying to 'create' some kind of narrative bringing together peoples' works, or many works by the same creator.

I had to contact a well-known curation team recently, as they had upvoted and curated a post that was blatantly fake-news spam-n-scam. Clearly that one slipped through to the keeper (sorry for the Aussie cricket reference)...

Yes, curating requires a degree of expertise in the subject matter. Don't up/down-vote a post (or even write one) on circumcising blue whales if your expertise is in the physics of hydronic heating.