why is "que" in this sentence
Usted tiene que salir ahora. you have to leave now.
Why is "que" in that sentence? what word does that represent?
the use of "que" is confusing sometimes.
tener +que is a periphrasis (phrase) than mean "to have to".
If you used deber instead of tener que then the que would not be there. Think of it like hay que where the two words are used together to mean "ought to"
Unfortunately, there is no answer to this question. It's like asking why "turn out" is in this phrase "turn out the lights" since we are neither turning the lights nor taking them out of any container. And, yet, "turn out" when put together means "switch off" but who knows why?
Likewise, Spanish speakers don't seem to know why "tener que" means the same as "deber" (deber means must in English).