Spotlights are all video posts, strung together to make a long-form piece on a given topic. It’s not certain which hashtags the Instagram team will choose, but it’s safe to say trending items will get some attention.
It’s a nifty way to pinch a bit of thunder from Twitter’s Moments, and is a lot like Tumblr’s similar feature in search. Like both platforms, any content the Instagram team uses is attributed to its creator.
If you’re not seeing the feature yet, give it some time. Instagram appears to be rolling it out incrementally.