A paper wallet contains a public and private key pair for making crypto transactions. It is generally created with a key generator program and printed on paper as two strings of characters and two QR codes. It is not recommended to use paper wallets if you are looking for the most secure solution to storing your Bitcoin. This is due to the fact that it requires passing your private keys through a printer that may or may not be connected to the internet. There are now more secure methods of storing your Bitcoin, such are hardware wallets.