Cole:
If you take a sheet of paper and a ruler and draw two parallel vertical lines on it. And two parallel perpendicular line to the first two, these lines could represent a post and an intersecting tie beam. A detail drawing could show the joint used to connect these two timbers, either exploded or together with dotted lines.
I'd be happy to email you some examples.
A rendering of a completed drawing is where the program creates a surface that looks like wood and applies that to the 3-d drawing so that the finished drawing would look like a real timber frame structure.
Again, I'd be happy to email you some examples.
I'm not sure if there are courses in your area that offer this type of training.
My advice to you would be to first learn about timber framing from books on the subject. Then try and learn how to draw the joints.
You can learn AutoCAD or any CAD program while your reading and learning about timber framing, then once you understand timber framing and have learned CAD drawing you can try to draw some joints.
If you go to the guild home page and select Publications from the pull down menu, then Joinery, then Historic you'll go to a page where you can download (for free) a series of works by Jack Sobon showing all kinds of joinery details.
This could be a good place for you to learn and understand how frames have been put together in the past. This series is also available in printed format from the guild online store, for $10 or so.
Good luck with your studies.
Jim Rogers