As you can see. All my own (and connected device to my googleaccount) devices are listed here...
If i now would buy a new device and use it also with my google-account... At setting up the device i have to choose google account. I will use my account. The device will now syncronize with google...
In this sync ALL MY apps will be installed in the new device...
If i buy or install a NEW app (and already have registered more devices) then it is installed only on the selected device in google play... But i can continue with install it again and select the other device to install