Most people describe a tension headache as a constant dull, achy feeling either on one side or both sides of the head, often described as a feeling of a tight band or dull ache around the head or behind the eyes. These headaches usually begin slowly and gradually and can last for minutes or days, and tend to begin in the middle or toward the end of the day. Tension headaches are often the result of stress or bad posture, which stresses the spine and muscles in the upper back and neck. Tension type headaches are the most common, affecting upwards of 75% of all headache sufferers.
To sum up: if you sit at a desk all day and hunch in front of a computer screen, the headaches you suffer from are most likely “tension” related.