Ok, here's the science and the best I can tell how it relates to "freebase cocaine" aka "crack"(as best as some ditzy blonde can describe - feel free to call me out if I make a mistake!)
"Freebase" is a chemical term meaning basically "the main chemical is not a 'salt'." 'Salt' meaning the product of reacting a base with an acid. In a safe lab, etc, mixing sodium hydroxide and Hydrochloric acid will give you table salt and water (starting with the right amounts, etc) , other starting chemicals yield other salts. In this case the Sodium Hydroxide could be considered the "base" that is reacted with an acid to yeild a salt. (Cocaine base plus HydroChloric acid (HCl) yeilds Cocaine HCl, or "powdered cocaine" as it is known, although both base and powder can look about the same, they don't act the same esp. their water soluability.
Specifically of interest here is "Cocaine Freebase" or "Methamphetamine Freebase" which could be also called cocaine paste (appears as a white paste even when very pure), or Meth Base (appears as an liquid oily substance when pure). React those with HCl vapors and you get Cocaine HCl or Meth HCl, which are the powders most are familiar with, and are both 'salts' as we say. "Salts" dissolve good in water usually, freebases often don't. Thus the desire for Cocaine HCl when in an sniff'a line mood or when wanting it to dissolve in water.
But if smoking is desired, swim has to look at the vaporization temperatures vrs. the temps at which the chemicals themselves start to burn/degrade. Turns out Cocaine HCL has a very very high vaporization temp, so high it'll mostly burn before vaporizing, wasting most of what one has. Cocaine Freebase doesn't have this problem, it vaporizes at a low enough temp. to allow a significant amount to go into vapor and into swim's lungs/bloodstream...but won't dissolve in water, so no good to snort.
(Numbers from Wiki) - "Crack vaporizes near 90 °C (194 °F),much lower than the cocaine hydrochloride melting point of 190 °C (374 °F)" and that's not even the vaporization point of Cocaine HCl, it's just the melting point. Burning of product occures. If soym ever felt anything from this it is most likely either some cocaine got based in the flames or they inhaled some of the powder before it burnt.
Meth vaporizes at a medium temperature between the two extreems of Cocaine.
Meth also has a freebase, but unless you make it large-scale you'll probably never see it. Why? 'cause the Meth HCl seems to vaporize to a good enough extent without it all burning that we don't need to mess with trying to make/use Meth Freebase (oily liquid hard to deal with, so its much easier to have 'powders' unless you're IG Farben or someone...). I think it'd be rather low-boiling, probably could be used effectively; but without a good reason like the difference between the two cocaine's vapor pressure, the availability of Meth FreeBase will most likely never take off.
So, no matter what it's called, Coke base is the smokin' type, Coke HCl is the snortin' type, and it don't matter with meth (and most anything else one can vaporize successfully) if you've got the base or a salt as it'd dosn't affect the vaporization temps that much.