If you spend some time in an English-speaking country you might hear the term "etiquette". It means normal and polite social behavior. This may seem like a difficult word at first, but it can be very useful to understand.
Etiquette is not the same in every culture or in every situation. For example, standing very close to the person you are talking with is quite common in some Asian countries. However, if you do this in Europe, some people might feel uncomfortable. Even in China, we all know that etiquette is not the same in all situations. Perhaps we think that talking loudly in our own homes is fine, but there are other places where talking loudly is not allowed. For example, most people would agree that talking loudly in a library, a museum or a movie theater is impolite. Even if you are with your friends, it is better to keep your voice down in public places.
If we see someone breaking the rules of etiquette, we may politely give them some suggestions. One of the most polite ways is to ask someone, "Would you mind doing this or Would you mind not doing that." People don't usually like to be criticized, so we have to be careful how we do this.
Although rules of etiquette can often be different, some rules are the same almost everywhere in the world! For example, dropping litter is almost never allowed. If you see someone you know doing this, you can ask him, "Would you mind picking it up?"
