How Do Wine Grapes Differ?

"By the way, is there a big difference in say Chardonnay and Chablis or between Chardonnay and Riesling?

Define "big difference." There are usually some consistent characteristics that give most wines made from Chardonnay grapes, for instance, a family resemblance -- kind of an apple-like or tropical-fruit quality and a rather rich, full body. Riesling wines are most often made a little sweet, and I often find kind of musky, canteloupe aromas in them or even something aromatic like a nice whiff of pine needles. Sauvignon Blancs are usually very dry and tart (which is why they're so good with fish or seafood, but a little harder to like all by themselves), and they tend to fall into either of two categories: Citric, like grapefruit or lemon-lime, or "grassy," an odd but pleasant scent that might smell like fresh-cut grass or green beans or asparagus or even green chile peppers. I like that kind of Sauvignon Blanc, myself!

It's similar among red wines: Cabernet Sauvignon is usually a dry, tart table wine with aromas that might remind you of black currants or sour cherries, and it's often "tannic" (astringent) in flavor when it's young. It makes a great match with beef or lamb. Zinfandel is full of fresh berries and immensely fruity, so it's really easy to like. Merlot, currently very popular, is somewhat similar to Cabernet but generally softer and more sippable. It often reminds me of black cherries.

This is just a starter, but for those who want to follow up, there's a chapter in my online Quick Wine-Tasting Course that goes into a little more detail about the major wine grapes and how they differ.

"Chablis" is a little different story. It's not a grape. In France, it's a Chardonnay made in the region called Chablis, and it's fairly expensive. For a long time, inexpensive white wines made in the U.S. were called "Chablis" also, even though they weren't made from the same grape. Nowadays, this practice has almost died out, except for a few "jug" wines like Almaden Mountain Chablis (which is a pretty nice cheap picnic wine, by the way), so you won't see an American wine called Chablis much any more, and if you do, you're probably better off to avoid it.