Device ID and Token
Just like the API key is your project identifier, the Device ID is your device identifier where each device gets a unique device id in the form of
_devicelg0lej2u4x490ijkgkq82okq_. The device token then acts as your password/access card which you use to tell the server that you have access to control the device. It can also be used to revoke access to particular device in the future or change access levels of a particular user.
You get the device ID and token when you register a new device.