It's really simple. All WDW visitors can book ADRs 180 days out (with some rare exceptions for events with different booking windows).
On property visitors (staying at a Disney resort) can book at 180 days out, BUT you can book for the next 10 days of your trip with that one phone call. If you're not an on-property guest, you would have to call every day (180 days out) for each day you wanted a reservation for.
However, WDW is changing their policy from 180 to 90, at least for some period of time. Check some of the other threads here where this is discussed more extensively. I assume that "+10" for on-site guests will continue, but do not know that for sure.