Exporting serial data from Arduino in real time

Thank you for your responses. I have a few of follow questions. In the documentation below, it has the lines defining a ledService and BLEByteCharacteristic. Can they be any string of letters and numbers? Does it need to be the same? Does it need to follow a certain format? Are these both for different types of connections (regular bluetooth and bluetooth low energy)?

Lastly, what function(s) in the BLE library transmit data?

https://docs.arduino.cc/tutorials/portenta-h7/ble-connectivity/