“Headache” is an extremely common symptom. Virtually everyone experiences one at some time or another. The vast majority of cases get better on their own; others have special treatments that can be helpful, and on rare occasions people die.
We define Headaches by their time frame. Select whichever one interests you, for the clinician’s condensed thought process when face-to-face with a patient. At the end of each will be a link to a full text with in-depth discussion.
Don’t forget that a person with either “chronic” or “recurrent” headaches can get a different kind of “acute” one.