While it is true that crack cocaine does contain the freebased form of cocaine, the term crack is specific to a kind of freebased cocaine made using a safer, cheaper and easier method than would normally produce pure freebased cocaine.

Pure freebased cocaine requires the use of flammable solvents, and thus is more dangerous and difficult to produce. Instead, to produce crack, powdered cocaine is mixed with sodium bicarbonate (better known as baking soda) and water and boiled until a solid substance separates from the boiling mixture. This substance is removed and allowed to dry, and then broken up into chunks, or "rocks."

One gram of powdered cocaine will typically convert to about 0.89 grams of crack cocaine. The Drug Enforcement Agency (ie take this number with some doubt) estimates that crack cocaine is about 75% to 90% pure cocaine.

Crack cocaine is a form of cocaine that is smoked in a glass pipe. Because the cocaine is immediately absorbed into the blood through the lungs, this creates an incredibly fast high.

It should probably be noted that this stuff is exceptionally addictive, and generally considered really nasty stuff. It's also extremely rather illegal.