Upholstered chairs are upholstered: they have a covering of material and are a lot softer to sit on than unupholstered ones. Any kind of chair can be upholstered. An easy chair/armchair is certainly upholstered! It would not be comfortable otherwise. For example, in my house I have a nice comfortable upholstered computer chair in my office, and lots of upholstered furniture (sofa and armchairs) in my lounge. I have a little upholstered easy chair in the dining room, and six unupholstered dining room chairs (of just wood). So, in summary, your office furniture can be upholstered, or not. As you choose. Your sofa is almost certainly upholstered! It would be very uncomfortable otherwise! Ouch! Your easy chairs and armchairs are probably upholstered too! Or they won't be comfortable!

What material is the seat of your pants touching? If it is touching wood, the chair is not upholstered. If it is touching cloth, leather, or similar material, the chair is upholstered. In an automobile, the seats are always upholstered. An office chair in which the seat can turn or pivot is "a swivel chair." A swivel chair may or may not have wheels. The wheels are often called "casters." Nowadays a swivel chair would usually be upholstered, but I have seen (very comfortable!) wooden swivel chairs that were not upholstered. An "easy chair" is an upholstered armchair that is thickly padded. All of the fabric and padding on a chair are the "upholstery." When it wears out, you might send the chair out and have it "reupholstered."

I happened to see this a few days ago: http://s10.postimg.org/kjca9zxuh/DSC02634.jpg The chairs in front are upholstered. The chairs in back are not upholstered.