How ThingsBoard linked/refer the device in the system?

Question

This is not exactly a problem I am facing. This is more of a clarification/explanation I am looking for, but not getting any clear answer.

In ThingsBoard (IoT platform) when a device is registered, user gives a unique name to it. The system automatically generate (and probably attach) a 'device Id' to it. There is also another information linked to a device, that is device's 'access token', which can be system generated or user can create one manually. When data is sent to the system, we need 'access token' to access the system, along with 'hostname'. The data is registered in the DB (postgreSQL in this case) for each device with its 'entity_id' which is actually the 'device Id' that system generates. So, these THREE:

 (1) user given device name
 (2) system generated 'device Id'
 (3) system generated or user created 'access token' 

seems linked.

While identifying a device in Rule Engine, or in other setting inside the TB system, I could simply identifying them as their names I have given. But the device itself does not know by which name it is identified in the system. How the system knows that which data is coming from which device? So, my guess is that above mentioned THREE information are linked. Could anyone please confirm/clarify about it? Or how ThingsBoard's inside system worked about this device identification.

Thanks.