You have few options when you post on Hive.
- Keep rewards, this is standard
- Send all rewards to @null (burn), everyone still receives curation rewards as normal
- Decline rewards, post makes no rewards, curators make no rewards
- Send rewards to DHF, this donates them to be used with Hive Proposals
- Send to a third party
This post is sending all rewards to @null, so the post earns rewards normally, when the post pays out, the blockchain auto sends all the rewards to @null and burns them. This reduces the amount of Hive being created by a small amount.