Subtractive synthesis
Sound design by sculpture: start with a harmonically rich waveform and carve away what you don't want.
An oscillator produces a sawtooth or square wave packed with overtones, a filter (usually a resonant low-pass) removes the top end, and an amplifier shapes the volume over time. Filter and amp are both driven by envelopes such as ADSR and by an LFO. The VCO → VCF → VCA chain comes from Robert Moog's modular systems of 1964, and the Minimoog (1970) packaged it into something you could take on stage.
Moog's patented ladder filter, 24 dB per octave, is still what people mean by "fat analogue". The model is intuitive enough that nearly every synth interface is drawn after it, even when the engine underneath is wavetable or something else entirely.