Levels
A level is a horizontal reference: each level has an elevation, and most architecture sits on one.
What a level is
Walls, floors, roofs, columns and equipment have a Level field. Changing it moves the element to another level. Each level has its own plan view.
Create a level
Open Context → New level, or use the + in the view tabs. The new level gets its own plan tab.
Elevation
Select the level in the project browser to edit its elevation in meters. Elements on the level keep their offset from it.