A hoppy, moderately strong pale ale. English style versions have less hop character and a more pronounced malt flavor than American/New Zealand versions which feature hops very promenently. Brewed to survive the voyage from England to India. The temperature extremes and rolling of the seas resulted in a highly attenuated beer upon arrival. English pale ales were derived from India Pale Ales. A pale ale brewed to an increased gravity and hop rate. Generally will have more finish hops and less fruitiness and/or caramel than pale ales and bitters. Fresher versions will obviously have a more significant finishing hop character.
Several variations of the style exist. Session IPA - Lower alcohol (under 5%), but with a big hop character. Imperial IPA - More hops, more alcohol. Typically over 8%. Usually assertive in their hop character.
Black IPA - IPA flavours and aromas, but black in colour. Some may have a slight roast malt note from the use of black malts, but not to the same degree as a porter or stout.