It is the toxin produced by the Botulism Bacteria. It is a neuro toxin that is one of the deadliest toxins known. It is usually produced by improper canning food. The bacteria has to grow in an oxygen free environment to produce the toxin. The canning process has to be hot enough to drive out the free oxygen, but not hot enough to kill the bacteria for it to form.
I do not know the process used to deliberatly make it.
It works because it causes total paralysis of muscles. It is only temporary when used cosmetically and needs to be redone almost monthly.
The amount used has to be very carefully measured and tailored precisely to the individual. this is one of those times when there is very little difference between an effective dose and a fatal dose.