Revit Fundamentals and the User Interface
Start with the project environment: the ribbon tabs, the Properties palette, the Project Browser, the View Control Bar, and the status bar. Understand that a Revit project is a single database file, and that everything you see (plans, sections, 3D views, schedules, sheets) is a view onto that same model. This is the single most tested idea: editing a wall in a plan changes it everywhere, and deleting a level deletes the views hosted on it.
Know the element hierarchy: categories (Walls, Doors) contain families (Single-Flush), which contain types (36" x 84"), which contain instances. Type parameters drive all instances; instance parameters drive one. Questions love to ask where a parameter lives.
Traps to watch: temporary hide/isolate (the glasses icon) is view-specific and resets when you close the view, whereas permanent hide and visibility/graphics overrides persist. Worksets are not layers and do not control visibility the way layers do in CAD. The Project Base Point and Survey Point are different objects with different behaviors when clipped or unclipped. Selection cycling (Tab) and the Options Bar context changes trip people up. Also know that linked models are not editable in the host, and that Purge Unused only removes truly unused types.
Rule of thumb: before answering any UI question, ask "is this setting stored in the view, the type, or the project?" If the answer is "the view," the change will not follow you to other views.
Worked example: a candidate is asked why a wall shows in a section but not a plan. The likely answer is a view-specific category override or a plan region, not a modeling error, because the model is shared across all views.