Paper wallets are an offline cold storage (extra-secure storage that does not make contact with the internet) method of saving cryptocurrency. In simple terms, it is printing out public and private keys on a piece of paper which you can store and save in a safe place. The keys are printed in the form of QR codes and letters which can be scanned in future for all your transactions. It gives complete control to the user and so is considered safest option to store cryptocurrency for long term. User does not need to worry about the well-being of a piece of hardware, hackers or any piece of malware and just need to take care of a piece of paper.
There are only few cryptocurrencies that offer paper wallets. Find below list of websites to generate paper wallet.