The 'traditional' way of CAD for architecture is to draw a bunch of lines and circles, much like you'd draw a plan by hand, but on a computer. This is very error prone and labor intensive. Your client asks you remove a window, you need to remove it in several views etc.
The holy grail of architectural CAD is in a part of what is loosely called 'BIM', Building Information Modeling. You make a 3d model of a building and generate separate views on that, like cross sections and plans, but also use that same model to do e.g. earthquake simulations or energy efficiency analysis or cost estimating. Autodesk has a product called Revit that purports to do this, but it has a long way to go to really fulfill the 'BIM dream'.
This is a subject near and dear to my heart - working with architects and contractors who run around with A0 format paper copies of plans, who do cost estimates by measuring, with a rule (!) each room on the paper plan and calculate areas with a calculator on a piece of paper, it makes me die a little bit inside each time I get a quote and I see the areas or dimensions or whatever different for each fricking ocntractor, instead of using software that would do pretty much everything that they just spend a day on in a few seconds.