I confuse the terms: Apple ID with Password

Your Apple ID has one password. You use this password on each of your devices to access your account on those devices. You can also use that password to interact with Apple on web-based services such as Manage your Apple ID or to Get Support.

Separate to that, your devices have their own passcode which is required to open the device to use it. Typically on an iPhone, for example, it will be a code of six numbers, or you can choose to have a four number code. You can choose to make the code the same on each of the devices or different on each of them.