This command effectively locks the wallet by removing the encryption key from memory. Once executed, any further access to methods requiring wallet access will necessitate calling 'walletpassphrase' again to unlock it.

How is this used?

The walletlock command is used to enhance the security of the wallet by locking it when not in use. This prevents unauthorized access to wallet functions and funds, especially in situations where the wallet is not actively being used for transactions. It is a recommended practice to lock the wallet when it is not in use to prevent unauthorized access and potential theft.