Here's a catchall post on Things I've Learned by osmosis:
VM = Vegetable Matter. This is a polite way of describing the straw, seed pods or burrs you might be expected to find in an animal's fleece. Thus a wool preparation might be described as having 'minimal VM'.
"Roving" is wool prepared to spin, usually at a wool mill, where it is carded by machine and pulled out into lengths and wrapped in balls or cylinders.
"Top" is also wool prepared to spin, but it is combed rather than carded, which aligns the fibers more parallel to one another.
If you want to spin 'bouncy', stretchier knitting yarn, you need roving. If you want to spin 'tight' smooth thread, you need top.
Spinning yarn with a lot of give, from roving, is spinning 'woolen'; spinning tight, less-stretch and less airy thread is spinning 'worsted'.
[Disclaimer - there are big long technical discussions about the difference between spinning woolen and spinning worsted, but that's the laymen's gist of it.]