Out of the phone numbers that exist, which one is yours?
vs
What is a phone number? (that is yours)
I'm sure someone can come up with a better example, as I am only quasi-fluent 😜 And I am certainly not an expert on Spanish grammar.
I see it as similar to how we ask "What time is it?", but if you say "Que tiempo es?" instead of "Que hora es?", they won't know you're asking about time, and will probably tell you the weather.
The words may translate directly, but the meaning doesn't. This is why all translations should be looked at with suspicion.
