What is it? it's a Synth of sorts. Serge is module based synthesis. Each box is a set of patch channels allowing for different combinations of sounds...you can make synth patches, bleeps, bloops, atmospherics, and noise.
So I took one bloop of a sound, added a distortion VST, and did a bit of filtering and looped the tail end of the WAV file and I got this amazing bass tone.