What is the difference between different wines?!

What is the difference between different wines?

Other than grape varieties what is the difference between different wines? For example, what's the difference between Moscato, Semillon, Verdehlo, Chard, a "classic dry white", riesling etc? Also, what justifies the enormous value of wines such as Romanee or Chateau D'Yquem? Is it prestige, rarity or is the wine genuinely more enjoyable?

Primarily it is the grape variety -- because the question you ask is the difference between wines made from various different varieties. (Of course there are otherfactors such as where the grapes are grown, and how the wine is made and aged that means one Chardonnay will not taste exactly the same as another)

What justifies the enormous value of wines such as Romanee or Chateau D'Yquem? Primarily market demand. These are wines made in a finite quantity and more people want them then there is availability.

d'Yquem is always going to be in short supply because first off it comes from a limited size vineyard. But then it comes from grapes in that vineyard that have been affected with 'noble rot' (or botrytis), a naturally occuring fungus that happens in certain conditions which attachs to the skins and extracts the water from inside the grapes leaving only a shrivelled raisin contining a minute amount of sweet grape essence. So tiny amounts are made of an incredibly sweet wine. (If the botrytis doesn't happen then they make a dry white wine from the unaffected grapes which is sold under the label Ygrec).

I think it is genuinely very enjoyable, but it is a bit too pricey for me. Because it is very famous and so many people want it, the price is high.