The bluetooth logo is shown below:

The Bluetooth icon/logo.
The Bluetooth icon/logo.

Advanced Audio Distribution Profile (A2DP)

This is a bluetooth standard which supports the streaming of audio between bluetooth-enabled devices.

Bluetooth 4.0

An attribute is a piece of labelled and addressable data. A characteristic is a group of attributes, and a service is a group of attributes.

attribute < characteristic < service 

Bluetooth 4.0 uses the server/client paradigm.