Apparently it produces an intense high quickly, but the effects typically do not last very long.
For example, cocaine powder is cocaine hydrochloride, a water soluble salt. Being water soluble means that you can snort it, eat it, inject it, or plug it (put it up your ass) and you will get high. However, a cruder form of cocaine is cocaine freebase (i.e. crack), which is not water soluble and therefore cannot bet eaten or snorted. You must smoke it to feel the effects.
It's the same with methamphetamine. Meth freebase is an oily liquid, which your body cannot absorb, so the only way to get high from it is to smoke it. Crystal meth, however, has been converted to a water soluble salt, and can therefore be snorted, injected, etc.
The heat used to smoke freebase drugs generally destroys a large amount of the active drug you are trying to consume, therefore it is NOT an efficient route of administration. However, the high generally has a faster onset, and the physical act of smoking is generally pleasurable, so that's why we have people becoming addicted to crack. The duration from smoking crack is much shorter than the duration from snorting coke, but again, people like smoking things, so people enjoy crack. You'll actually get higher for longer if you snort cocaine hcl vs. smoking crack.
this is done by putting your drug of choice (or drugs) on a peice of tin foil or a metal spoon, lighting it from underneath and sucking up the smoke through a straw (rolled up bills work to)
the effects are amazing, but usually short-lived.
She picked up the pecan pie on the way home because she felt like freebasing.