The technical description of mineral oil is "a mixture of aliphatic, naphthalenic, and aromatic liquid hydrocarbons that derive from petroleum." In layman's terms, it comes from crude oil, and it could be described as a hodge-podge of non-toxic stuff from crude oil that we can't burn as fuel very easily and has little other use.
We get
lots of chemicals from crude oil. Among the lighter hydrocarbons we get butane (4 carbon atoms, or C4). Gasoline is C8 (octane!). C10 to C14 is diesel fuel, C12-C15 is kerosene, jet fuel and motor oil are in there somewhere, and C20 to C40 is wax/paraffin (like in candles). Beyond that you get tar, asphalt, and my personal favorite Bunker C.
Mineral Oil is a mixture of C15s to C40s. It's cheap because the refining process makes a lot of it. And now you know where it comes from and what's in it, sort of.
