Where does the steem rewards come from?

Im sure the answer im looking for is to be found in eigther the whitepapiers or some other info on steemin.info, but i thought i might be faster to ge someone who knows to explkain or popint me to that spesific part.

The reason im asking is mainly because i dont completely understand (or rather unistand, to use a more comprehensive wording) how this all work together. As when we upvote, we dont use steem or steem dollars, yet the author of the article gets Steem and Steem Power. So the platform itself pays that out to the author. Does that mean that there is a continues flow of generated steem crypto currency? In the same manner as Etherium have no max number that can be generated..

If not then what happens when there isnt more to "take from"? OR is there a function where that steem flows back to the platform without the platform having to buy it back?

As to me the only current reason steem have a value, as in people having a reason to buy it, making it abel for others to sell what they earn; is to get influence on the plattform to reward the once they upvote more, and ahve more effect on downvotes.

Aside from some that may use it as a intermediate to pay someone for something in steem via the platform.

Not that im not aware that compared to manny other cypto currencys, Steem and SBD is actually faster very easy to use as a payment. Im just not 100% on how the reward system works in relation to how steem is generated. So who ACTUALLY pays the authors for what the most influantial users deem the most worthy? I guess is kinda what im asking.