The Name of the Game is Paralysis.
There are seven botulinum toxins in all, identified by the letters A through G. Once a toxin has latched onto a nerve ending, the chemical responsible for starting muscle contractions (acetylcholine) is blocked. That's because these toxins go after the proteins that release acetylcholine.
In the simplest terms, botulinum toxins keep your body from telling its muscles to contract.
This can be very dangerous. For example, the toxin can cause respiratory failure by obstructing messages from the body telling your lungs to breathe. But what if you want to keep a muscle still?