Okay, so you know how when someone smokes a cigarette, it makes smoke that can be breathed in by other people who don't want to breathe it in? That can make them sick and give them problems with their lungs and breathing.
Well, some people got together and decided that it's not fair for smokers to make other people sick with their smoke. So they made a rule called a smoking ban, which means that people aren't allowed to smoke in certain places.
For example, they might say that you're not allowed to smoke inside buildings like restaurants, stores, or offices. Or they might make it so you can only smoke in special places outside.
Sometimes people don't like these rules if they like smoking, but the hope is that it will help keep everyone healthier and feeling better in the long run.