Health education is any planned learning experience designed to help people make informed choices about their health: a talk on hand-washing at a school, a one-to-one session with a newly diagnosed diabetic patient, a poster campaign on tuberculosis symptoms.
Health promotion is broader. It includes education, but also policy, environment and services: a tax on sugary drinks, smoke-free public places, safer roads. The Ottawa Charter of 1986 set out five action areas for health promotion, and only one of them, developing personal skills, is mainly educational.
The distinction examiners want in one line: health education changes what people know and can do; health promotion also changes the conditions they live in. Health education is one tool inside health promotion.
For health promotion models such as PRECEDE-PROCEED and the health belief model, and for the epidemiology behind choosing a priority, see the public health page.