Correlation Meter displays the phase relationship of a stereo signal.
A correlation of +1 (the far right position) means that the left and right channels correlate 100%—they are completely in phase.
A correlation of 0 (the center position) indicates the widest permissible left/right divergence, often audible as an extremely wide stereo effect.
Correlation values lower than 0 indicate that out-of-phase material is present, which can lead to phase cancelations if the stereo signal is combined into a monaural signal.