A headache can be described as a pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions. This occurs in migraines (sharp, or throbbing pains), tension-type headaches, and cluster headaches. 
It is worth noting that due to its lacks of pain receptors, headaches are not caused by pain within the brain tissue itself, instead, headaches are caused by disturbances of the pain-sensitive structures around the brain.
Headaches are most commonly induced under the influence of heavy dosages of stimulating compounds, such as traditional stimulants, certain psychedelics, and certain dissociatives. This holds particularly true during the offset of the experience and if the person is dehydrated or has not eaten enough food.
- Head ache disorders (World health organization) | http://www.who.int/mediacentre/factsheets/fs277/en/