Yes and yes. Effectively the founders of Steemit have invented a new currency called Steem. A certain amount ~$100k worth is distributed every day to writers and content creators and commentors. Then this amount of Steem can be sold on the external market in exchange for Bitcoin. This Bitcoin can be sold for USD or other currencies.

Where does this incoming money come from? Mostly investors who believe in Steem's value as a crypto-currency and store of value. The total amount of bitcoin in the world is worth ~$10 billion. Similarly people who buy Steem Power are investing in "shares" of the Steemit. Given that Facebook is worth ~$350 billion - investors are speculating that if Steemit grows to that size they will profit significantly.

A lot of the value of Steem is speculative at the moment. But as the site grows, it will grow in value. I hope that answers your question.