A general practitioner (GP) is the first point of call for treatment when you are ill. They are trained to care for and treat the whole body. If you register with a GP they will get to know you well and will be able to advise you most effectively. Try to always see the same GP.
There is another benefit to being registered with a GP: if you are ill you can call the practice at any time and make an appointment to see a doctor soon. Many health insurance funds also charge cheaper premiums if you are registered with a GP.
There are various ways of finding a GP: ask your friends and acquaintances which doctor they see, look in the telephone directory or look on the Internet.