The EXC!TE SNARE DRUM plugin has two columns of parameters. One one side, you have the "Excitation" parameters which pertain to the modeling of a drum stick that is striking the drum head, and the "Resonator" which refers to model of the actual snare drum itself.

Velocity - has a "variance" knob which adds randomness to the MIDI velocity fo each note giving your drums a more life-like performance by introducing random loudness (human drummers are not perfect robots when it comes to playing at a specific volume).

The other excitation parameters have both sliders and variance knobs for intensity and randomness.

The exciter feeds into a waveguide resonator algorithm which lets you change drum head tuning, snares tension and hit position via the sliders.