Passwords on an iPhone are stored in the device's keychain, which is a secure storage system for passwords and other sensitive information. The keychain is designed to protect this information using advanced encryption techniques, which helps to ensure that it is not accessible to unauthorized users.When you create a new password on your iPhone, whether it's for an app, website, or other service, the device will automatically save it to the keychain. This allows you to easily access the password in the future without having to remember it.The keychain also stores other sensitive information, such as credit card numbers and personal information. All of this information is protected by a master password, which is set by the user. This password must be entered every time you want to access the keychain, and it is important to choose a strong and unique password to protect the security of your information.You can access the keychain by going to the Settings app and then selecting 'Passwords & Accounts.' Once you're in the Passwords & Accounts, you can see all of the passwords that are stored in the keychain and manage them, including adding new ones, editing existing ones, and deleting ones you no longer need.It's important to note that the keychain is device-specific, which means that your passwords will not be synced across multiple devices unless you have iCloud Keychain enabled. iCloud Keychain is an Apple feature that allows you to sync your keychain across multiple Apple devices, such as your iPhone, iPad, and Mac.In summary, Passwords on an iPhone are stored in the device's keychain, a secure storage system for passwords and other sensitive information. The keychain is protected by a master password that is set by the user, and all the passwords can be accessed and managed under the setting.