Some ECUs cannot be directly read. This feature is simply not implemented by the manufacturer because he never needs to read the content of the car’s ECU, only flash it for updates. So, the virtual read is the only way to read the ECU data. The virtual read file is an original file that corresponds to the software number of the ECU actually installed in the car. Virtual read is fast, the file is instantly downloaded from the server in a couple of seconds. With this virtual read, even if the car is tuned, if you read the car, you will always have an original file.
It’s the real readout from the car’s ECU. So if the car is tuned, you read the tuning file, if the car is original, you read the original file.