It is actually known as cold storage which can be used offline. This wallet (Paper Wallet) is public and private key printed together. It is highly secure and there is no possibility for this to be hacked. It is made of paper where information is printed. Sometimes plastics can be used for durability. In this paper private and public keys are printed. You can copy and paste the keys onto a text document and print it out. Or free web services can also be used. Key generation process is done here by browser. With few wallet services you can cut, fold and seal. You send your bitcoin to the open location showed on the wallet and after that store it in a protected place.