Why do people get headaches? like what causes them.

Various causes: Headaches could be a rather simple annoyance or very complicated. There are many factors causing headaches. Also, a headache could be a sign of another disease process or be the disease itself. Some examples include simple tensions headaches, vascular headaches (e.g. Migraine), tumor related headaches, spine related headaches, etc. A qualified physician needs to assess this properly.

Most come from Neck: 85% of all headaches come as an extension of neck issues. It could be from muscular tension, joint arthritis, dental issues. The symptoms can be one sided or both, mild or even severe. Can be occasional or daily. Regular headaches, when left untreated, can lead to severe symptoms, that include light sensitivity, nausea or dizziness, which are "secondary migraine" features. Treat the neck!