Private Keys vs. password

[baggage]

When Bitaddress generates your private keys for an offline paper wallet,  is that your only password (the private keys) or is there any other reason to
invent a password for the paper wallet?

[grue]

a private key can be password protected using BIP 38.

[DualSignal]

Your private key is an encryption/decryption key known only to you. With this key you are able to do everything you can with a bitcoin address (spend, sign etc).

Using bitaddress.org:

Paper wallet - WITHOUT BIP38:
You are only given private keys that you must store

Paper wallet - With BIP38:
Your private keys are given encrypted and you must store the encrypted private key and the passphrase

Brain Wallet:
Your private keys are determined by the passphrase alone so you only need to store the passphrase (passphrase needs to be very strong to avoid brute force attacks)

[baggage]

Thank you gentlemen!

[Abdussamad]

Brain wallets with human generated pass phrases are not recommended.

If you want something like a brain wallet install electrum on an offline PC. It'll be much safer and have more features too.