Campylobacter species (spp.) are Gram-negative, curved, S-shaped, non-spore forming and motile rods with a single polar flagellum. They represent the most common causes of human foodborne gastroenteritis. Campylobacter colonizes the gastrointestinal tract (GIT) of a wide variety of domestic and wild animals, particularly chickens, turkeys and pigs, which are considered the main reservoirs of this bacterium. Campylobacter is transmitted to human, mainly through ingestion of contaminated poultry meat, unpasteurized milk and polluted water, causing severe abdominal pain, fever, fatigue and diarrhea. Nevertheless, little knowledge about the biology and pathogenicity of Campylobacter spp. is known rather than other predominant pathogens. Therefore, we reviewed the biology of the bacterium, its survival, growth characters and the factors related to its pathogenicity and the mechanisms by which the diseases are happened in the view of the available literatures. Furthermore, we illustrated several techniques used for Campylobacter spp. epidemiological classification.