A stud wall, as opposed to a brick or block wall, consists of a wooden frame, which is then covered with plasterboard on either side and
plastered (or tiled). It's a popular way of building internal walls because they are cheaper, quicker and lighter (which affects what needs to be
underneath in order to support them). A stud wall should look indistinguishable from a brick/block wall, but the giveaway comes when you knock on
it. Stud walls are hollow, although you would usually fill them with rockwool or similar to provide both thermal and acoustic insulation.
I built one such wall behind the kitchen sink isthmus, but the biggest task of this type was the walls to divide the former kitchen/diner into a bedroom, an ensuite shower room and a separate cloakroom to be accessed from the first floor landing.
An extension of the same sort of skill as studwork, but a usually bit less uniform and hence more interesting/challenging, is the boxing in of pipes or other infrastructure that needs to be hidden. I did a lot of this, at varying scales. In the Family Room, killing two birds with one stone, I boxed in the extractor vent pipe from the cloakroom and the sprinkler pipe which had to go below ceiling level to get under the steel beam that replaced the ground floor rear wall of the house.