A friend’s wood table had a water stain on it. Said friend’s mother applied Vaseline to the stain, and – poof! – the table was good as new in a matter of days. It was a new stain, which probably hadn’t been there for much more than 24 hours.
Why? How? Does Vaseline contain wood-restoring properties that I just haven’t known about? Might it fix burn marks, too? 
Water stains occur when water gets under the varnish. Applying denatured alochol to the stains draws the water up from under the varnish, so I’m guessing vaseline might do the same thing, but I’m not sure how.
Sorry… I hit submit before I was finished.
Although I’ve found a few sites recommending vaseline as a stain remover, none of them give the ‘why’ behind the application.
Well, it is petroleum based…and other oily products are commonly used to displace a stain - everything from veggie oil to mayo. I think the oil gets in and displaces the stain/water.
Burn marks are actual scorched fibers of wood, whose chemical properties have changed. Typically, the only solution for a woodworker is to remove the burn mark, usually by sanding. Therefore, I find it highly unlikely that burns can be removed via vaseline or similar trick.
A true ‘stain’ is the presence of one or more materials mixed in with the desired material - in this case the wood/finish - and remover are best when they displace the undesirable material and leave the desirable material unharmed.
Do you think W-D40™would do the same, without as much mess?
It would leave a stain of its own.