In America when people meet each other for the first time, they talk about things like weather, family, work, school, or sports. They ask questions like "Do you have any brothers or sisters?" "Where do you work?" "What school do you go to?" and "Do you like sports?" They also ask questions like "Where do you come from?" and "Where do you live?" These are polite questions, not personal questions.
But some things are personal or private, and questions about them are not polite. People don't ask questions about a person's salary (薪水). They don't ask how much someone paid for something. It is OK to ask children how old they are, but it is not polite to ask older people about their age. It is also not polite to ask people questions about politics (政治) or religion (宗教) if you don't know them very well. People don't ask unmarried people "Why are you single?" and they don't ask a married couple with no children "Why don't you have any children?"