VCO : Saw and Pulse waveforms plus SUB octave selectable Square/Pulse waveform by switch, PWM for pulse width modulation and related CV input, 1V/Octave for pitch, Hard Sync and FM input.
VCF : special filter with self-oscillation, usually it happens with high resonance setting, you'll see a red LED glowing in the middle of the waveforms switch, therefore turning such switch to middle position it'll allow you to use its sine wave using 1V/OCT input for pitch.
CUT for modulate cutoff frequency.
EXT IN is for external input.
ENV controls the amount of the internal envelope that affects the cutoff frequency.
REL controls the envelope decay/release; when no cable in VCA input the internal envelope controls the VCA.