There are two general Style classifications for Pipes: Straight & Bent.  A Straight Pipe has a straight Shank and Stem and will be more inclined to directly transmit heat and moisture to the palate.  A Bent Pipe has a curved Shank and Stem and tends to collect more moisture at the bottom of the Bowl, below the bend of the Shank.   Both Styles   have a distinct feel and balance in the hand and mouth, which Pipe smokers appreciate for different occasions or moods.