When I was in school in the Mesolithic Age we actually drew on this thing called paper with devices known as pencils. Now days art students often draw on electric tablets or monitors even though we encourage our students to stick with the paper and pencils for a while longer. But all of this technology has not only sped up the illustration process and made it much easier to make corrections - it's also made it much easier to teach!
The Cintiq monitor by Wacom or other pressure sensitive graphics monitors have enabled teachers to perform "draw overs". I just started doing draw overs last year for both my online and UVU students. In the past I had to do a little drawing off to the side of my students work - it was good but really doesn't compare to actually drawing on top of their drawing to show what decisions I would have made. If I had done that on an original drawing on paper it wouldn't allow for seeing the students drawing without my "drawover" - in other words the original drawing would be altered forever with my crappy drawover on top. The student would have had no way to continue working on their drawing after my critique.
It is amazing for teaching online because we're only dealing with sketches that have been scanned and emailed to us. We have to be able to show our students what we're talking about - so this technology has actually been a key factor in us being able to teach online. Above you can see some of my UVU students work (draw a polar bear / Viking) and my rough little drawover which doesn't go into detail but focuses on general construction. It makes teaching so much more satisfying and - fun!...Thank you Wacom!