What is a GP for?

I tried to get an appointment at the doctors and was asked by the receptionist, 'Is it a medical emergency?'.

I thought A&E or a walk in centre was for medical emergencies but some friends argued you should only try to get a GP's appointment if it's a life threatening situation. I don't think they are correct.

The only way to get an appointment at my surgery is to phone up on the day so who are you supposed to see if it's not a medical emergency but you need to see a doctor and a pharmacist isn't appropriate?