How does this E-stim work?

[Toodo]

Hello, im not new in this world. Im a big fan of Cock Hero vids and PMVs for years.
I absolutely love it. But lately i see more and more about E-stim here?
Can anybody explain me how it works? It gives pulses on the beats? It reacts to the beatmeter? Am i right?

And can anybody tell me what i have to buy to start doing this?

Thanks allready

[throwawayacct]

Couple threads here, so we're not re-treading old ground:

viewtopic.php?t=26126

viewtopic.php?t=24422