Fiio BTR3 is a Bluetooth receiver, usb dac and headphone amp. It will most often be used to power a wired earphone or headphone and connect by Bluetooth to a phone. It can also be used to add a quality Bluetooth connection to powered speakers and as a usb dac for a computer. High quality built in mic and 11 hour battery life.
Fiio BTR3 has all the latest Bluetooth connectivity codecs, so you will have the best sounding bluetooth connection regardless of the phone or computer source you use: it has AAC (mainly for iPhone), apt-x, apt-x HD (many new android phones and its very good), LDAC and LL (low latency, so the sound syncs with video/skype calls).
The BTR3 sounds better than basic Bluetooth receivers since it takes the signal from the bluetooth chip and runs it through a higher performance dac/amp to drive the headphones. This provides a clearer and more powerful sound.