All Proof of Stake consensus algorithms are using masternodes. A masternode not only stores all the data of the blockchain, but also has a minimum number of coins that is locked up. With this, a masternode helps with certain tasks/functions on the blockchain, for example verifying transactions, or helping with consensus, providing privacy features or others. For some cryptocurrencies, these have a higher weight in the vote on updates. For providing these functions in a Proof of Stake consensus algorithm, masternodes receive rewards from the respective cryptocurrency.