Frequency: It's the cut off frequency. All frequencies higher than the specified value will be cut off from your voice

Resonance: The 'amplification' level of the frequency that you sepecify in frequency parameter.

For example on a scale of 1 to 100, if you specify frequency: 50, and resonance: 80, all frequencies higher than 50 will be cut off, and the '50' frequency will be amplified to level '80'. These values are different for each instrument. You will need to refer to parameter tables for that.

Formant: It's the voice character, changes timber of your voice.

To change gender of your voice, change the 'tuning' or 'transpose' parameter.

I hope this helps.