If you are using an iPhone, you will often be asked to enter your password / passcode. Even though the number of models that support Face ID for face authentication and Touch ID for fingerprint authentication has increased, a passcode is always required at the first startup after the system is shut down, and a website that requires login is required. Input is indispensable when using. If you forget it, troublesome situations such as reissue procedures will occur.
There are two strong passwords / passcodes that you shouldn't forget on your iPhone, or can be cumbersome to forget. One is an "iPhone passcode" that is entered immediately after unlocking or restarting the system, and the other is an "Apple ID password".
The iPhone passcode is a 6-digit number used to confirm unlocking. It is not necessary when Face ID / Touch ID is enabled, but when face authentication / fingerprint authentication fails, iPhone is locked for more than 48 hours immediately after turning on the iPhone or when the system is restarted You will be prompted for input when it has not been released. To change, go to "Settings"-> "Face ID (Touch ID) and passcode".
An Apple ID password is required for Apple online services such as iCloud and App Store. In addition to changing the settings in "iCloud" or "iTunes Store and App Store" in the "Settings" app, you may be asked to confirm the settings when using the service, such as purchasing an app. Note that if you forget your Apple ID password, you will not be able to use these services.
In addition, there are passwords that are required to use websites and apps, but you need to forget your iPhone passcode. Those passwords are usually stored in the “iCloud Keychain”, and if you use Face ID / Touch ID, you can immediately check them on the “Settings” → “Passwords and Accounts” screen. There is also a “screen time passcode” to set up family iPhone usage, but in terms of importance, it is not equivalent to the iPhone passcode and Apple ID.