text: There are MANY types of headaches...with several different origins. The most common one is the tension headache, which originates in muscle spasm in the neck and shoulder areas. Others include things like migraines, cluster headaches, and they are also a common feature in many other illnesses like the flu or other generalized infections. They may come from muscular sources, vascular sources (in the blood vessels of the head or brain), or--RARELY--from increased pressure inside the head from something like a brain tumor or fluid mechanics problem.  Most headaches are simply a nuisance, though some can truly be debilitating, and NOT related to any serious pathology.