Arrow heads are the sharpened tips of arrows. In modern terminology they might be called points.
In prehistory they might be simply fire hardened point of the shaft itself or might be made of stone. Metal heads replaced these and might be of a number of varying types. The end of the head that joins the shaft might be tanged (such as is found on typical Viking Age arrows or many Eastern arrows) or socketed as found on later medieval arrow heads and most modern points.
Tanged arrows have a greater tendancy to split the shaft when they strike the target than socketed arrows.