A longbow is a type of bow. It may not have been as strong as a crossbow, but it could shoot more arrows per minute. Also, the basic equipment cost little, and could be easily mass produced. Metal-tipped arrows could go through armour. Only the strongest armor would stop it. Archers (longbowmen) would usually have a second weapon, often a battle-axe, if the fighting came close to them.
The longbow was mainly used in the Middle Ages until the 1500s.