Pitch is the source
Fundamental frequency is measured in Hz. Faster vocal-fold vibration produces a higher perceived pitch; slower vibration produces a lower pitch.
Resonance is the filter
The throat, mouth and nasal cavities emphasize different frequency bands called formants. Their shape and effective length influence whether a voice sounds bright, dark, large or small.
Use both concepts
Lowering pitch without balanced resonance can sound forced. Conversely, resonance changes can make a voice sound deeper without a dramatic change in median Hz. This is why a pitch test is informative but not a complete voice rating.