Dentistry is the widely used "practical application of knowledge of dental science (the science of placement, arrangement, function of teeth and their supporting bones and soft tissues) to human beings." I'm sure you can see why in most countries, many years of training are required in university in order to become an actual dentist. A dentist is what we call a professional practitioner of dentistry. This "Dentist" has normally studied between 4-8 years at university and will normally also have alot of practical experience with working on actual patients, often times accompianed by a more experienced dentist.
Dental Public Health - Which is the study of dental epidemiology and social health policies
Endodontics - Which is root canal therapy
Oral and Maxillofacial Pathology - Which is the study, diagnosis, and often the treatment of oral and maxillofacial related diseases
Oral and Maxillofacial Radiology - Which is the study and radiologic interpretation of oral and maxillofacial diseases
Oral and Maxillofacial Surgery - Which is the extractions and facial surgery
Orthodontics - Which is straightening of teeth
Pedodontics - Which is pediatric dentistry for children
Periodontics - Which is treatment of gum disease
Prosthodontics - Which is the replacement of missing facial anatomy by prostheses such as dentures, bridges and implants
Often times visiting the Dentis is an un-nerving situation. Rest assured that if you are going to a qualified dentist, they have all of the training that is required to perform what it is that you require. If you are still un-easy or having a problem choosing a dentist in your area, you might want to talk those around you and find out who has had good and bad experiences and where.