This tag should be used for any question that's about the Demoman class from Team Fortress 2, Valve's free-to-play team-based multiplayer shooter.
TF2's Demoman is the class designed to blow stuff up. Heavily geared towards the task of putting out indirect explosive damage, the Demo's long-range detonations can wipe entire teams and demolish enemy buildings with ease.
The Demoman has high health, below-average footspeed, and two weapon slots that fire explosives - a grenade launcher and a stickybomb launcher. Grenades deal big damage on a direct hit regardless of distance travelled and can be bounced around corners for safe damage without risk of counterfire. Stickybombs can be set up on target zones or near enemy buildings and detonated all at once to clean the area of any opposition. However, as the Demoman lacks any bullet-based weapons, he has trouble hitting nimble targets and cannot fight at close range without going melee or inflicting self-damage. Still, the raw power of his explosives makes a skilled Demoman an equally huge threat, and is in fact one of the two classes limited to one player in competitive play due to two Demos being able to keep a symmetrical map locked in stalemate.
Alternatively, the Demoman can be used as a pseudo-class known as the Demoknight, which swaps out his stickies for a charge attack and involves wielding a sword as his primary weapon. Demoknights can still use grenades depending on loadout but will mainly be focused on melee battling, making them much less efficient at demolishing enemy fortifications (a task which many players expect out of a Demoman).