Low Frequency Oscillator. A way to modulate the filter, that works on it's own. Like the envelope follower, but dependant on time and not signal volume. Like the sweeping of a phaser.
Works well width the phaser settings, the peak-notch filters. Slow lfo's work better with high resonance or 4-pole filters, fast tend to work better with 2-pole. IMO.
Try the stepped shapes with the vocal filters.
. LFO's are fun ^^