Smoking is an addiction caused by nicotine in cigarettes that leads to many harmful health diseases. The substances in cigarettes often cause cancers like lung cancer as well as other diseases and health problems. These include heart disease, emphysema, pregnancy complications, gum disease, and more. Cigarettes contain nicotine, carbon monoxide, hydrocyanic gas, ammonium, sugar, and cocoa along with filters. Different types of smokers are identified like chronic smokers who smoke constantly without awareness, and passive smokers who are affected by others' smoking.