Each voice comes with a multi-mode filter with various "flavours" of filtering (low pass x 2, band pass x 4, high pass x 4). Each filter has a dedicated envelope generator and LFO for the cut-off frequency.
A filter passes through certain frequencies while making others less (or not at all audible). A filter's slope (often measured in dB) specifies how quickly frequencies are affected around the cut-off frequency. For example, a 24db filter is much more dramatic in the way the frequencies are affected (attenuated) than a 6db filter which affects frequencies more gradually.
It is important to note however, that the filters in your Woovebox were designed for musicality and maximum sound design versatility/"flavoring" as found in vintage analog gear, rather than cold clinical and - some would say - boring "perfection" as found in some more naive/"perfect" implementations of digital filters.