There are many reasons why we get head aches. A headache is defined as pain in the head that is located above the eyes or the ears, behind the head (occipital), or in the back of the upper neck. Headache, like chest pain or dizziness, has many causes. Headaches are most thoroughly classified by the International Headache Society's International Classification of Headache Disorders (ICHD). This classification is accepted by the WHO.
The head is one of the most common sites of pain in the body.
The most common types of headache can be classified as 1) primary, 2) secondary, and 3) cranial neuralgias, facial pain, and other headaches.
The most common types of primary headaches are 1) tension, 2) migraine, and 3) cluster.
Tension headaches are the most common type of primary headache and usually are treated with over-the-counter medications for pain.
Secondary headaches are a symptom of an injury or an underlying illness.
Why a headaches are caused it is not well known.
Please take your time to go to the next link and you will find plenty of information about headaches. You can also look on Wikipedia where more can be read about this interesting topic.headache-medicine