如何理解 where are you based?

It means, roughly speaking, 'Where do you you live?' or 'Where is your home?'. You wouldn't interpret it as 'Where are you from?' if you no longer live in the place where you grew up. You're based in the permanent place where you live now. The idea of being 'based' somewhere is used mainly by people who travel for their work. You might say that you are based in London, because that is where you live for most of the time and that's where your family live and where your company's Head Office is. So even if you have, say, an apartment in Paris where you stay sometimes when you're working there, you're still based in London. It means that where are you live,or something about your residence. = Where are you currently living? 对的， based in 是一个常用词语，用来询问常驻在哪里。如果一个英国人常驻在上海工作，则问where are you from?就得回答英国。如果问where are you based?就得回答上海。