The idiom “when in Rome, do as the Romans do” implies that when one is visiting a new place or culture, one should adopt the customs and behaviors of that place. In other words, it’s about adapting to one’s surroundings and showing respect to local customs and traditions.
People often use this phrase to suggest that there’s a certain way to behave in specific situations, environments, or cultures, and it’s best to conform to those norms for the sake of harmony and understanding.