The spear is a long stick with a point on the top, like a javelin, which is often thrusted or stabbed at people instead of launched/thrown. The point is either the sharpened end of the stick or there is a pointed (and often bladed) metal head attached to the stick. It was a very common weapon used by both nobility and the common soldiery, both on foot or whilst mounted.
A long spear designed to be wielded soley in the hand from horseback is called a lance.
One legend of the Battle of Stamford Bridge is of the berserker who, armed with a daneaxe, held the bridge alone, and was only killed when an English solider floated under the bridge in a salting tub and speared him through the planks of the bridge itself. This legend is the origin of the Spear Pie, a Yorkshire pastry shaped like a boat.
Spears in the SCA
Spears in Re-Enactment
In re-enactment spears are common, particulary in Dark Ages groups as they were a common weapon. They are sometimes used two handed when evidence would suggest otherwise, as it is easier to wield. The absence of missile weapons such as javelins and arrows in combat for safety reasons has lead to this inappropriate state of affairs.
The practice of "pool cueing" (thrusting a spear with the back hand whilst allowing the front hand to guide or sometimes removing the hand altogether) is prohibited in most Australian re-enactment combats, due to its inherent dangers.