This tag should be used for any question that's about the Pyro class from Team Fortress 2, Valve's free-to-play team-based multiplayer shooter.
The Pyro is a short-range ambush class. Most of the Pyro's weapons are only effective at close range, and any exceptions can only deal sporadic damage to distant targets. As a result, playing an offensive Pyro requires use of ambushes to take enemies by surprise and disorientate them with a stream of fire to the face before finishing them off with a weapon of choice.
The Pyro's primary weapon is a flamethrower that sets enemies ablaze, dealing enough damage to force lighter classes into retreat. The flamethrower also has a compression blast ability, releasing a pulse of air that can repel enemies and reflect projectiles. Secondary weapons take the form of shotguns (which are more effective at close range) and flare guns (which can set things on fire from a distance but fire slowly and usually deal low damage). Combined with melee weapons that encourage lighting up enemies and then swinging away, the Pyro excels at close-range combat but is ineffective at medium range and beyond (barring the occasional reflected rocket or arrow).
While classified as offensive, with above-average health and ambush-heavy design, the Pyro easily fits into defensive or support roles as well. Using the airblast to push invulnerable enemies and projectiles away from friendly buildings can thwart attacks without much trouble. The Pyro is also the best spy-checker in the game, as one puff of flame will instantly reveal enemy Spies that are cloaked or disguised for several seconds, and some of the Pyro's melee weapons can help squash chaos caused by a Spy's Sappers.