That question is very vague and general, do you have something specific in mind? The Spitfire was a fighter aircraft, and thus was tasked with shooting down enemy aircraft. Of the two principal fighter types available to the RAF during the battle, the other being the Hawker Hurricane, the Spitfire was the more modern, and was capable of engaging the primary German fighter aircraft, the Bf-109E, at even terms. The Hurricane was an older design and was at a disadvantage against the Bf-109 in an even dogfight; the ideal tactics were therefore to concentrate the more capable Spitfires against the enemy fighters while the Hurricane squadrons went after enemy bombers with their slower, but more stable aircraft. In practice, however, air combat was very fluid, so you would often have Spitfires attacking bomber formations, Hurricanes taking on fighters, etc. Like I said, is there something more specific you would like to know? A fighter aircraft is tasked with shooting down other aircraft, not much more to the role than that.