Standard housing includes rooms that are a bit larger and, in some cases, are in buildings that have been recently constructed or renovated. The "dorm" option in standard housing refers to rooms that house four people.
Standard housing rooms can be found in these buildings...
... and they look something like this:
Single room, Radcliffe
Double room, Arbor House
Double room, Bill's Place
Double room, Radcliffe (only one bed shown)
Double room, The Pines
Dorm room, Dorm 54 (4 single beds--only 2 shown)
Dorm room, The Pines