Weapons are used as self defense, they can either be wieldable items that fire projectiles (guns in this case) or melee weapons (e.g. knives). A player starts with 2 weapons (a knife and a pistol) or 3 (a knife, a pistol, and an assault rifle, if you also have Castle Miner (This promo code has been removed, now you get Creative Mode if you enter the promo code from Castle Miner) when they spawn on a world for the first time. Anything that could be used to inflict damage upon an enemy could technically be classed as a weapon, although certain weildable items aren't suited for use in combat (e.g. a Pickaxe, which is meant to be used for mining).