Blended and Varietal Wines

At the basic level, the difference is quite simple. Varietal wines are made from a single grape variety, while blended wines are made using two or more.
The most obvious example is the difference between the two great red wine styles of France. Burgundy red wine is composed of the single variety Pinot noir. Bordeaux red wines are most often blends of up to five varieties, Cabernet sauvignon, Cabernet franc, Merlot, Malbec and Petit verdot. There are a few Bordeaux wines made from a single variety, but they are the exceptions that prove the rule.
So much for theory. The distinction between varietal and blended wines is less clear in practice. Many varietal wines are made from blends of wine grown in several regions. Australia’s iconic Grange is such an example. Each year hundreds of samples from many vineyards are tasted and evaluated before the final blend is decided upon. The result is a blend of regions, rather than varieties.
Many more modest Australian wines with lesser claims to fame are also regional blends. The process of selecting the blend is similar but much more simplified. The clue on the label is often the words “wine of South Eastern Australia”. This is almost as general a statement that you can get about the origins of an Australian wine.
Some wines made from a single variety are blends of several different vintages, but this is quite rare for table wines.
While on the topic of labels, you should be aware that many wines bearing a single varietal name can legally contain up to fifteen percent of other varieties. If the wine is labelled as a blend, then the variety with the largest percentage composition should be named first, for example wine labelled Cabernet Merlot, should contain a greater percentage of Cabernet than of Merlot.
Our second question is “does it matter?” Well, if you find a wine that you enjoy and it is a blend, then you should continue to drink it. Blended wines are not "second class" wines. The finest champagnes are made from several varieties of grapes!
However, if you wish to extend your wine knowledge and thus enhance your wine experience you should try varietal wines whenever possible. There are hundreds of varietal wines available, each with a special subtle difference waiting for you to discover.

from: http://www.chiff.com/