Cocaine freed from impurites by treatment (usually with ether) by heating it to produce vapors for inhalation. When you create freebbase you neutralize the HCI, leaving you with pure cocaine. This is commonly confused with crack, which is typically 2 parts cocaine, 1 part baking soda and a little water heated gently to form crystals, which the user then smokes/inhales. Both are derived from cocaine and the effects are similar but freebase and crack are not created equal.
While watching a friend create freebase cocaine:
"Man, I thought freebasing and smoking crack was the same thing. Naw, dude. The freebase is the pure stuff. Crack ain't worth shit."