Oh Debbie, you really shouldn't encourage me!
However, since you have....
I visualise the difference - perhaps someone who really knows can correct me - as a stroke causing damage to a specific area of the brain - that fed directly by the blood vessel that has become blocked. The amount of damage caused depends on how far down the 'trunk' of the blood vessels is the blockage.
Dementia seems to cause more widespread, random, damage all around the perimeter of the brain.
Where a localised area is damaged - as with a stroke - it may be possible for an adjacent, undamaged area to learn to take over some of the function.
Where damage is more general, it may be difficult for the function to be reassigned, especially as the damage seems to affect more than the memory storage capabilities alone.
Another thing is that strokes come as catastrophic incidents, permitting - often - some time for recovery between strokes, if there is more than one.
Dementia - Alzheimer's, in particular, seems to be a continuing process, slowly - and sometimes not so slowly - over time.
Dementia - vascular, is caused by mini strokes and thus takes on some characteristics of the stroke pattern, though often the vascular dementia is accompanied by Alzheimer's as well.
I'm looking forward to hearing other views on this........