What are two kinds of smoke produced by tabacco?

* Mainstream smoke: This is the smoke that is inhaled by the smoker. It contains a high concentration of tar and nicotine, as well as other harmful chemicals.

* Sidestream smoke: This is the smoke that is released from the end of a cigarette or cigar. It contains even higher levels of tar and nicotine than mainstream smoke, and it can also be harmful to nonsmokers who breathe it in.