The word "ban" means to prohibit or forbid someone from doing something. It’s frequently used as a verb:
Many restaurants and hotels now ban smoking. (You can’t smoke in those places.)
The government bans the use of certain chemicals because they are too dangerous.
Bill was banned from the bar because he got into too many fights. (This sentence is in the passive voice. The word "ban" is often used in the passive voice.)
A majority of Americans believe that assault weapons should be banned.
You will be banned from this chat room if you misbehave or use foul language.
The word "ban" is also commonly used as a noun:
There’s a ban on smoking in almost all public buildings in the United States.
A ban on watering lawns was put into effect during the drought. (drought = no rain)
There was a ban on alcohol consumption in the United States between 1919 and 1933. Most Americans refer to this time as The Prohibition. It was illegal to drink alcohol during the prohibition, but a lot of people broke the law. Organized crime increased as a result of the ban.
Gangsters created a lot of illegal businesses during the 1920s.