The OBject EXhange (OBEX) protocol was originally designed to allow file transfer over infrared links, these are using light pulses in the infrared spectrum region.  Current use of OBEX
In recent times OBEX has been seen as a way to transfer files to mobile phones without the need for physical connection. Bluetooth has been adopted by many devices, however many devices Only support the OBEX Push operation. This means you can only send a file to the phone.
For more information, see Creating a Bluetooth server running OBject EXhange (OBEX) protocol