A crossbow is a ranged weapon using an elastic launching device consisting of a bow-like assembly called a prod, mounted horizontally on a main frame called a tiller, which is hand-held in a similar fashion to the stock of a long gun. Crossbows shoot arrow-like projectiles called bolts or quarrels. A person who shoots crossbow is called a crossbowman, an arbalister or an arbalist (after the arbalest, a European crossbow variant used during the 12th century).
Crossbows and bows use the same elastic launch principles, but differ in that an archer using a bow must draw-and-shoot in a quick and smooth motion with limited or no time for aiming, while a crossbow's design allows it to be spanned and cocked ready for use at a later time and thus affording the wielder unlimited time to aim. When shooting a bow, the archer must first fully perform the draw, holding the string and arrow while pulling them back with arm and back muscles, and then either immediately loose without a period of aiming, or hold that form while aiming. When using the heavy bows suitable for warfare, both actions demand some physical strength. As such, the accurate and sustained use of a bow in warfare takes much practice.