It stands for Bring Your Own Device which devices are owned by students.  Even though they are purchased through school bulk purchase schemes or from retail shops.

BYOD profile is simply a tag to a device.  Device Name is physically attached to the device, whereas BYOD profile is a set of information attached to the ESP Student app which is installed on the device. 

The purpose of BYOD profile is to identify the ownership of the device.  Such information cannot be displayed in TeacherPad＋, and only can be seen in ESP Student app on the device.