To add to BrettM answer, Bluetooth is the RF standard on which many protocols can stack up; each such protocol is called a 'Bluetooth Profile'.
The Bluetooth model you purchased comes only with the Serial Port Profile (SPP) profile implemented in the firmware. This mean that you can use it for establishing serial communication.
As serial protocol will probably be too slow for stereo Audio over Bluetooth, Audio usually use a different profile called Advanced Audio Distribution Profile (A2DP). Unfortunately, the HC-05 does not come with this protocol stack implemented in its firmware. If your primary goal is to send stereo Audio over Bluetooth, consider purchasing a dedicated chip, such as XS3868 or Sparkfun's RN-52. For beginners, it is recommended to get one with a breakout board for easy integration with Arduino projects.
For completeness, there are many other Bluetooth profiles, each is optimized for different task. See Wikipedia for the full list: