These paper wallet use to have the private and public key for an address printed usually. Some clients and software will generate this for you to simply writing it down.
If you are planning on depositing a amount of bitcoins to the different wallet, make sure paper wallet has some good ones outlined on their site. Keep in mind that anybody who knows the private key can access the bitcoins stored in it as their own now or at any time in the future. It's important that only you and the recipient are aware of what the private key is!
They could potentially lose some of the balance if they only transfer a part of the balance off the paper wallet.
I won't suggest this especially send by email. Safest option is sending a btc to someone via btcnetwork.