You can buy a straddle if you predict volatilities to rise or think there will be large unexpected moves in the underlier but you are not sure about the direction.
Long straddle consists of long positions in a call and a put of the same strike and expiry.
See also strangle.
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The screenshot shows the following portfolio:
European call struck at 11.000 with expiry in 30 days
European put struck at 11.000 with expiry in 30 days
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