Bitcoin wallet passphrase
Your Bitcoin wallet is basically a virtual wallet. Your wallet is identified by a unique wallet address that can be obtained from coinbase. So how is this wallet protected? It's basically by a pass phrase. When you download a bitcoin client, such as the bitcoin-qt, you can encrypt your wallet using a passphrase.An example of a bitcoin wallet address,
19tSiA1Rktrwu7hsUfGBtyYNTA667AwWwQ
This is my bitcoin wallet address. If you have this address, you can transfer bitcoins to this account using this address. However, in order for you to access the wallet, you'd need the pass phrase, which is a secret key entered by me. Without this, you would be unable to access the wallet.
IMPORTANT: If you lose your bitcoin wallet passphrase, your funds are lost forever. There is no way to recover them. So make sure, you write down your pass phrase at some place safe.