Public health concerns dealing with health issues that affect whole populations. This can include disease surveillance, policy management, education and so forth.

Think about major health issues that affect the public as a whole.

One major issue that comes to mind is OBESITY. This is a big public health problem because obesity leads to illness, and if you magnify one obese and ill person to a WHOLE POPULATION of obeses and ill people, that means you're going to have a lot of people filling hospitals, being out of the workforce because of illness, and a lot of tax dollars being spent on obesity-related diseases.