Serial communication

Hi all, I don’t understand concept of text in attached image.Please help me. Thanks

A long time ago in a galaxy far far away if you wanted to print binary data using an Arduino rather than ASCII data the syntax was

Serial.print(someData, BYTE);

Then in release 1.0 of the Arduino IDE the Serial.write() function was introduced which does the same thing and support for the BYTE parameter in Serial.print() was removed

See Serial.write() - Arduino Reference

Thanks UkHeliBob