What does Proof of Work (PoW) mean?
If you really want to know what PoW is, go to Wikipedia and Read the Full Article. For a Crypto-Newbie it is enough to know that PoW means that a Coin must be created through computational Power. This is called mining. Mining can be done through CPU, GPU (Graphic Card) or special Devices called ASICs which are build and optimzed for only a few Algorithms.
For Mining we will have a separate Topic in our Knowlegebase later.