How does vacation time work exactly?

I'm a young professional and so far I've only worked contract positions so I have not been eligible for vacation and therefore have no prior experience to reference from. Having not been in a full time position makes having this conversation with managers difficult as I would rather not have them misinterpret my curiosity.

So how exactly does one accrue vacation time? Are vacation hours allotted monthly that add up to a total? Do unused sick days go towards vacation time? I've always thought that when someone attains FTE they are sort of just GIVEN a set amount of vacation time they can then use when they've been working continuously for a reasonable length of time.

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