Tobacco is a massive worldwide industry, and every year 6.7 million tons of tobacco is produced. The largest producers are China, Brazil, India and the United States, in descending order. Tobacco is produced by drying the processed leaves of the Tobacco plant.
Tobacco use is legal in all countries, although many have restrictions on smoking in public places or restrict purchase to adults.
There is some ongoing research into nicotine use for treating ADHD and schizophrenia, but otherwise tobacco has no medical viability.
People smoke tobacco for a number of reasons, including to reduce stress. It is both a mild stimulant and a relaxant and many people report a positive interaction with alcohol. It used to be both heavily advertised and glamorized by the film industry, which no doubt paid a part in people starting smoking.
Tobacco contains nicotine, which is extremely addictive. It is also a major carcinogen and causes cancer in the lungs and mouth, and increases the risk of cardiac problems. It is a cause of a huge number of deaths.