Triptozym, he's describing Butane Hash Oil that has been whipped on a hotplate while purging to whip in air and expose terpenoids, therby creating the unstable wax/budder version of BHO, which in its sap/shatter form is stable.
The foil thing is nasty as hell, it's pretty ironic to smoke hash oil off hot aluminum like heroin, DMT, and meth users do.
The best way to vape wax/oil (or anything else you can vape/smoke off of foil) is with a pookie, an "oil burner." I've never used meth or DMT, but I bought a pookie because I heard my guy was getting some DMT in. The Deemster never came in, so I smoked top-quality wax/budder in the pookie, and it worked even more efficiently than a nail/dome or curve/pad setup, but it took too long for tiny hits (as would foil), so when it broke I never bought another one.
I now just dab 1-hit-per-session with a Tiny Tube w/ Ti nail/dome, but if I ever had to use foil to vape drugs off of, I would just head to my headshop and buy an "oil burner."