First of all, What is Modular Synthesis?
Modular Synthesis is a Category of synthesis which consists of individual modules connected by wires (These are called 'Patch Cords').
The connection of these individual modules create a patch. If you ever layed hands on a DAW, you will probably have already seen this word. Each output creates and sends out its own signal. This signal is a voltage which varies in strength.
When Mixing or Layering these sounds, you have endless possibilties, according to what VST/Synthesizer you use, there are infinite combinations you have - More so when resampled.
There are different types & sub-types of modules in this line of synthesis. Even similair modules or exact copies of the same modules will have different Inputs, Outputs and Controls on Various Models.
Generally, Synthesizers have different modules to help modify the sound, the following are most commonly found in every synthesizer :
VCO -Volume Controlled Oscillator- This will output a pitched sound (frequency) in a particular waveform, most commonly a Square or Saw, but they can vary from Squares, Saws, Rounded Saws, Sine and Triangle Waves.
Noise - This generates a static noise, similair to the sound of Cymbals or Rain - They are occasionally used to make Sweep Noises, or the latter-mentioned Cymbals. There are different types of noise, like White Noise, Pink or Brown Noise.
EG This triggers an Envelope Generator which produces a repeating (Looping) shaped pulse, Often recognized as
ADSR is Attack Decay Sustain Release - It provides the shaping of a sound in terms of Volume, Cutoff, Pitch, etc.
LFO - Low Frequency Oscillator (Dubstep Anyone?).This is similar to the afore-mentioned VCO, only at a rate of 20Hz or Below that. When Modulating the VCO, you create a tremolo effect, because the pitch starts increasing and decreasing at a fast yet recognisable rate.
S&H - Sample and Hold - This takes a sample of the input when a pulse is received and holds it until a subsequent trigger pulse is applied.
-That's all for now, I'll go more into depth and add some videos and links later ^_^