What is "mineral spirits"?
Mineral spirits goes by many names, including "white spirit" and "paint thinner", and is basically just a hydrocarbon solvent mixture. According to this Wikipedia article:  


  White spirit is a mixture of aliphatic and alicyclic C7 to C12 hydrocarbons with a maximum content of 25% of C7 to C12 aromatic hydrocarbons. A typical composition for mineral spirits is > 65% C10 or higher hydrocarbons,[6] aliphatic solvent hexane, and a maximum benzene content of 0.1% by volume, a kauri-butanol value of 29, an initial boiling point of 145 °C (293 °F) to 174 °C (345 °F), and a density of 0.79 g/ml.


There are also three different types based on whether or not it's undergone processing to remove sulfur, solvent extraction or hydrogenation. Then each type has a separate grade: low flash, regular and high flash grades. So with three different types each having three different grades, there are nine different sorts of mixtures that "officially" fall under the term white spirits, or mineral spirits.