I would add that this concept gets very distorted as its passed from person to person, better to start with the source.
I studied it long ago and concluded I didn't have the skills to profit from it. You need to have a quick trigger finger but I did document and see 100% moves in the oex puts which scam mentioned as his preferred vehicle.
You CAN time the market!
But only after you trash the big 3 myths.
Myth 1 - its possible to get every point of every move ...Myth 2 - you'll never have a drawdown ......Myth 3 - you'll never have a loss