Proof of Stake rewards are distributed via proportional to the “stake” that validators have in the economy as opposed to the work you can do. Your stake increases based on the amount of currency in your wallet and how long it’s been there. The greater your stake, the higher the odds are that you will receive a reward for the creation of the new block on the chain. In contrast to PoW where scarcity comes from processing power, in PoS, the scarcity comes from the currency itself.
As of June 2017, Ethereum is using a Proof of Work system. By the Serenity update the platform will be updated to use a Proof of Stake system. As we get closer to that release we will learn more details about how the PoS system will work in Ethereum’s implementation, known as **Casper**.