It's a way to get your piece in front of more people, and therefore, more "reads" to get paid on. It's distributed to a wide audience. My piece on the crochet granny square got boosted. It's paying me close to 50 bucks this month instead of a couple of dollars. I figure it's a way to make more money and improve my writing. There are loads of stories about it. Search for "boost criteria" to find out more. Here's a good one -

https://medium.com/deep-sweet-valuable/how-to-get-boosted-deep-sweet-valuable-3d7ab963a4c4