What does Proof of Stake mean?
If you really want to know what PoS is, go to Wikipedia and Read the Full Article. For a Crypto-Newbie it is enough to know that PoS means that a Coin must be created through a small computational Power without tradidional mining. You can only stake if you have some coins; if you have more coins, you will more often get additional Coins through Staking. To Stake, you need your Wallet to be open and unlocked for Staking only all the Time (24/7).
You will create new Blocks for the Blockchain with your Wallet and for this you will get the Staking Amount.