Turpentine was until recently the standard solvent for oil painters That has changed in the last decade or so and most painters I know you mineral spirits, a petroleum product, as their solvent.
Artists use a solvent to thin their paint and in the manufacture of mediums. It is still the preferred solvent for any medium containing damar varnish.
Turpentine is made from the exudate of various pine trees and derives its name from the terebinth tree which grows around the Mediterranean from which turpentine was originally distilled. Terebinth a relative of the pistachio is mentioned in the Old Testament, and Virgil's Aeneid. Various different pines give different qualities and varieties of turpentine. Venice turpentine, for instance is from the Western larch tree.
There were formerly many commercial uses for turpentine. It was made into a bewildering assortment of patent medicines such as the one pictured in the advertisement from the 19th century above. It was sold as a cure for pneumonia, diphtheria, toothache, headache, rabies and even cancer in both people and animals. It was to be applied to the skin and taken internally as well. Many cleaning products still contain turpentine today because of its solvent qualities and clean smelling pine odor. There are still patent medicines based on turpentine too. Vick's Vapo-Rub is one. Most of the industrial uses for turpentine have now been superseded with petroleum products.
Until about five years ago it was possible to buy a good quality turpentine at the paint store. Sadly, that is no longer the case. There are several ways of making turpentine. The old and best way was like making maple syrup. The pine trees were "tapped" (actually scored) so their sap could be collected. Generations of slaves toiled in the heat of the Carolinas and Georgia to produce turpentine. It was as nasty a job as any man ever had and often enough being sent to the turpentine farms was a death sentence. This sap was carted to the cities and boiled in a huge retort over a fire. The resulting distillate was bottled and used for paint thinner, lamp oil, and in the making of furniture polishes when mixed with wax. The navy used vast quantities of turpentine.
There is a cheaper way to make turpentine that is far less labor intensive than that. Stumps, bark, and branches are all ground up and the product of that is distilled and sold as turpentine. Technically that product is called wood turpentine. I believe that is what is now commonly marketed as gum turpentine. Gum turpentine smells sweet and piney, wood turpentine smells like benzine laced cadavers. If you open a can of turpentine at the hardware store today and smell it, it won't smell like Pine-Sol, it will smell like death. Don't buy that, and don't use it.
I recommend you use Gamsol. I use various species of odorless mineral spirits (OMS) but since lots of people are reading this I need to err on the side of caution and recommend the Gamsol. It contains far less of the harmful volatile hydrocarbons which evaporate and poison the air in your studio. Turpentine may cause skin and lung irritation, nervous system damage and kidney disease. I have never had an allergy problem with turpentine, but many people have. My own teacher, Ives Gammell developed this problem late in life and switched to mineral spirits because of that. The health risks being what they are, Gamsol is the best solution, I think. I do miss the pine smell of good turpentine though. I actually wore it as cologne in art school, it was highly effective there. God knows what I would attract if I tried that with the turpentine of today.