mineral oil = oil you can use, if it's food grade, for various applications, including baby oil, laxatives, cosmetics, medicine, wood working, etc.

mineral spirits = paint thinner, lighter than mineral oil and also evaporates easier. cannot be substituted for mineral oil since it's poisonous.

the main difference between mineral oil and spirits is that the spirits are lighter and that the oil is available in a food grade quality.

it's easy to confuse the two terms, but they are separate materials with differing purpouses.