Payoff is a V. Long gamma, long vega, short theta. Profits if the underlying moves far enough either way to cover the combined premium.
The trap that gets asked. Buying a straddle into a known event often loses even when the move happens, because implied volatility is elevated beforehand and collapses afterwards. The vol crush can outweigh the gain from the move.
A strangle is the cheaper version using out-of-the-money strikes, needing a larger move to pay.