As I understand it, the term PTO (Paid Time Off) covers vacation time, sick time, paid holidays, etc.

Edit:

I went back to reread the post you were referring to. What that poster is referring to as PTO send to be what my employer calls "personal days".

Where I work I get 20 vacation days, which are expected to be scheduled. We have a number of fixed paid holidays, and sick time. We also get 5 personal days. Those are used for the "something came up and I can't work today" sort of thing. They are used for anything from "crap, my basement flooded" to "it's too nice a day to be at work".