Proof of Stake cryptocurrencies are a means for individuals to mine or validate block transactions within the network based on how many coins he or she has. The more a person holds, means more potential rewards and with most PoS currencies, the groups or individuals with the most provide hubs for the network that promote even more rewards.
Proof of Stake or PoS currencies are coins held in wallets to confirm transactions within the network. This method doesn't require vast amounts of power to solve transactions like Bitcoin.
By holding stake coins, besides earning rewards the network uses wallets across the world to provide a system to verify each other which promotes security, stability, and efficiency.
Holders of stake coins hold these currencies in wallets and pools that help to speed up the network. Holders get staking fees for keeping the currency in wallets that help the network.