Headache is one of the most common physical complaints and can be caused by factors like stress, diet, hormones, caffeine withdrawal, and lack of sleep. There are several main types of headaches, including sinus headaches caused by sinus pressure, tension headaches due to tight neck and shoulder muscles, and migraines which often include nausea and sensitivity to light and sound. Diagnosis involves neurological examination, history taking, and sometimes imaging tests like X-rays or MRI. Treatment involves over-the-counter pain relievers, anti-nausea medication, and lifestyle changes to reduce triggers.