Unfortunately, there is not a lot of emphasis on Preventive Medicine in Pakistan. Most patients visit a doctor for urgent / acute conditions when they get sick. During this kind of visit the doctor takes care of patient's presenting heath need only.
In Preventive health maintenance visit, a person visits the doctor with no acute illness or complaints, but mainly to get a thorough examination and discussion of their long term heath needs. The idea is to find out possible hidden health conditons and possible future heatlh risks to the patient - through detailed history taking, physical examination and doing certain required preventive tests.
This way a hidden medical contiton, if found can be "nipped in the bud" and advise or treatment/s can be offered to prevent future illnesses and health issues. Also, preventive vaccines can be discussed and administered.
A preventive health check is usualy required every 1 or 2 years.