I was in the middle of tracing this low res graphic with the bezier and shape tool and these dimension guides began appearing (jpeg attached.) I apparently inadvertently turned a feature on and would like to turn it off because I find the guides distracting. I opened the "dynamic guides" menu and deselected everything but that was not it. I've never seen these before. What are they called and what is the purpose of them?
Hard to tell from the image provided. Are they "dimension" lines i.e. width & height?
That looks like a GPU issue. Restart comp and see if it persists.
Look to see if you have Alignment Guides checked on the View menu. Click to un-check and turn them off.