A straddle buys a call and a put at the same strike and expiration. A strangle does the same with strikes spread apart (a call above, a put below). Both profit from a large move in either direction - you're betting on volatility, not on which way price goes.

When they pay

These strategies win when the underlying makes a move bigger than the combined cost of both options. They're used ahead of events expected to produce a big reaction - though not knowing direction. If price explodes up or crashes down far enough, one leg pays more than both cost combined.

Why IV is the catch

Because you're buying two options, you're paying double the vega - and if you buy ahead of a known event, implied volatility is already inflated. After the event, the IV crush hits both legs. The stock can move a lot and you can still lose, because the move didn't beat the pumped-up price you paid.

A straddle isn't a bet that price moves. It's a bet that price moves more than the market already expects.

The realistic view

Straddles and strangles sound like a free bet on volatility, but the market prices the expected move into the premium - you only win if reality exceeds expectations. That's a high bar, and the double time decay works against you every day you wait. Powerful in genuine volatility surprises; a slow bleed the rest of the time.