This is a 7-band harmonic (overtone) graphic equalizer with multi-channel support (up to 8 channels, host setup dependent, if you are using audio host application supporting VST version below 2.3 only 2 plug-in channels will be available).
Overtone GEQ implements graphic equalizing by using a serie of bell-shaped EQ curves. So, when you boost adjacent bands the actual boost or cut may go over the visual setting. Beside equalizing, Overtone GEQ applies harmonic enhancement processing. That is why Overtone GEQ is comparably CPU-heavy: it uses 7 harmonic enhancement modules, one for each EQ band. This generates quite complex harmonic distortion.