The reward pool is fed by a set amount of interest. This STEEM is created, but not yet paid out which is called the reward pool. When people vote, the reward pool is consumed. When people are not voting, the reward pool can get larger.

Downvotes were as valuable as votes in the past. They were essentially burned. With the new STEEM system, the downvotes are earned based on the amount of SP you have. The top SP holders can downvote will amazing power without burning any of their valuable votes.