There are 4 chairs shown below. Two are Windsor chairs, two are not.
If you're just getting started with antiques, and furniture, the difference may not be immediately apparent.
The chairs above are not
The quickest way to determine a Windsor chair is to look at the legs... especially the back legs.
Notice on the chairs above how the back leg runs all the way up, beyond the seat rail and actually becomes the back support? From Wainscot style, to Chippendale style to Federal style... it's not a Windsor chair if the back legs support the back rest in some way.
Now look at the difference in the chairs below.
Being a Windsor chair has nothing to do with spindles or arm rests. In a true Windsor style chair the legs support only
the seat. Back rests, arm rests are all separate parts which are also connected to the seat.
Additionally true Windsor chair (at least antique ones) were never upholstered. Yes, it may have an added cushion, or someone in the 1950's tried to make it look more modern by nailing upholstry over the seat, but it wasn't there from the start.
It's just that simple.