A general practitioner (GP) or family physician is a physician who operates a general practice and provides ambulatory care. The terms General Practice and Family Practice are often used interchangeably, though the latter is becoming more common. The field is also referred to as "primary care".
A Family Practice physician is board-certified in Family Medicine. Training includes a focus on the family as well as treating an individual throughout their life stages. Family physicians complete medical school and do one year of internship and 3 more years of specialized medical residency training in Family Medicine.
Family Practioners do primary care (prevention) as well as secondary care (disease modification). Some also do minor surgery or obstetrics while others focus on Occupational Health or Sports Medicine.
Modified from Wikipedia's article on Family Medicine Licensed under GNU FDL