Balanced line
In telecommunications and professional audio, a balanced line or balanced signal pair is an electrical circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths, to ground, and to other circuits. The primary advantage of the balanced line format is good rejection of common-mode noise and interference when fed to a differential device such as a transformer or differential amplifier. The combination of a balanced line and differential signaling in audio applications is balanced audio and is commonly used in sound reinforcement and sound recording and reproduction.
Read on Wikipedia