Static Objects are one of the pillars of level building in the LevelEditor. An actual complete map file share in static objects is around 80%. A proper set of pieces will allow you to create all sorts of rooms and ambients.
The creation window is a bit more complex than the ones we have seen previously. In detail, its composed of:
Thumbnail: shows a little picture so you can see how the object looks like.
Defaults: showing right next to the thumbnail are the defaults for the current selected entry: shadows (on for shadow casters), collides (on for solid objects) and occlude (on for occluders). These are useful for speeding up placement, since they save the user from having to set the above properties one by one after placement.
More on Static Objects here.