Are the straddles the same as strangles and can we also use these strangles for directionless markets?

A slight improvement of the straddle is the strangle strategy. While the long straddle, buys the call and the put of the same strike price, the strangle strategy uses a higher strike for the call and a lower strike for the put. This gives you two advantages. Firstly, since you are widening the gap between the call strike and the put strike your premium cost will come down. Secondly, when you are expecting range bound markets, a short strangle will give you a much wider protection range as compared to a straddle. In practice, strangle strategy is a lot more popular than straddles for directionless markets.