Like its big brother Swirl, Swirl Mini is a polyphonic source-of-chaos which emits two correlated randomly-drifting values per polyphonic channel.
This can be useful for introducing variance between and movement within voices in a polyphonic synth, for example by patching the first value so that it modulates the pitch of an oscillator, and the second so that it modulates the resonant frequency of a filter.
Swirl Mini has a second mode in which it acts as a polyphonic wave-shaper, which combines wave-folding and ring modulation-like effects.
Unlike Swirl, Swirl Mini does not draw pretty multi-coloured plots in a visual scope, showing you what it's doing. If its behaviour seems opaque, try playing around with Swirl first - the underlying behaviour of the two modules is identical, but Swirl Mini is smaller and more CPU-efficient.