AutoCAD is present in both.
ARCHITECTURE has walls/doors/roof/floor/window/sections/details/con
Plain AutoCAD is aimed at no one and has none of these abilities built in: it doesn't know a wall from a line for example, or a door from a widget.
As Dean said, lots of differences. You can download it and use it for 30 days free. Try and see. For me, the detailing features alone are worth the price. If you're going to do architectural design in AutoCAD, I highly recommend using AutoCAD architecture. You can use as much or as little of the objects. Only downsides are fairly steep learning curve and upward only compatibility. Revit is the more complete BIM solution.
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