Origin
The origin of the idiom ‘When in Rome, do as the Romans do’ was first seen in print in 1777, in Interesting Letters of Pope Clement XIV.
Explanation
It means that it is polite and respectful to adapt your way of behaving when you are in a different culture or society. This means to cover your body when you go into a church, a mosque or any place of worship. Or it could mean that you should dress well if you are going to meet with well-dressed people. Basically, we use this expression when we want to recommend to someone that he behaves appropriately. Then he will be respectful and respected. It refers to the importance of adapting yourself to the customs of the people who are in a certain place or situation and behave like they do. It is something that you say to mean that when you are visiting another country, you should behave like the people in that country. People from different places have different ways of acting, so it is important to try to do things the way people do who are from the place that you are visiting.
Examples
At work everyone dresses very casually. I used to dress formally, but when in Rome, do as the Romans do.
Jase : Are you sure we should eat this with our hands? Mike : Why not? All of these people are eating it that way. When in Rome, do as the Romans do.