A mortar is an artillery weapon which fires explosive shells. The shells are known as (mortar) bombs. They are fired at targets which are close, as mortars do not have long range. It has a short barrel which fires the mortar bomb at a low speed high into the air to reach its target. They have been used since medieval times. Mortars are made in different sizes, from large and heavy mortars to infantry mortars which can be carried by just one soldier. They are called an indirect fire weapon because the bomb drops onto the target from above, rather than being aimed straight at it. Soldiers firing a mortar do not need to be able to see their target.