In regards to shatter, or "dabs"; It's made by passing a gaseous solvent (often butane, ergo BHO or Butane Hash Oil) through the plant matter that rips the THC

In regards to shatter, or "dabs"; It's made by passing a gaseous solvent (often butane, ergo BHO or Butane Hash Oil) through the plant matter that rips the THC off the plant to gather in a waxy solid at the end of an extraction tube. If done correctly, and the butane is purged from the end product. In general its probably quite a bit safer than combusting plant material, assuming the person that made the BHO did it correctly. Most of the usage is done with a glass bong, with the metal "nail" used as a method of pressing the wax to the heated glass.