This in of itself doesn't necessarily mean that it's a good wine, but it does show the level of detail certain wineries will go, to ensure that it's history is known. It also demonstrates the level of commitment that some wineries have to their own reputation. This is a good thing to look for in wines.
However, in practice, other have noted that many wineries desire the larger areas from which to choose their grapes. This gives them options that allow them to create a consistent wine, rather than a wine dependent only one vineyard. Think of it this way: You found a grape that delivered very specific and measurable characteristics that produced a very great wine. Would you want to be able to locate a grape that replicated those characteristics from several vineyards year after year, or would you like to restrict yourself to just the one vineyard? This is one aspect of the "brand vs. terroir" debate that Derrick alludes to in the comments.
So remember...the better you are able to pinpoint the location of where the grapes have been grown, the better chance you have of getting a quality wine. But this isn't a hard and fast rule, as many wineries desire multiple vineyards to choose their grapes from, but it is a good rule of thumb to follow if you are new to wines.
Think of the following scale - State, region, valley, county, city, district, vineyard. The more of these you can determine on a bottle's appellation, the better chance you have of getting a good wine.
Appellations: The same rules of specification apply, but instead of the cities and counties being important, often (but not always) the House/Family Winery names are more important to note.
Also, many French and Italian appellations often (but not always) have governing authorities that determine just what makes up a Burgundy or a Chianti. In France the Appellation d'Origine Controlee is the French system of designating and controlling both the geography and the quality of wines (as well as liquors and some food products, such as cheeses). It is also known simply as Appellation Controlee and often abbreviated as AOC or AC.
Appellations: Appellations typically do not disclose what kind of grapes are used in the wine. They'd rather be known for where the grapes are grown as opposed to what kind of grapes they're made from. That's not to say there aren't standards...there are. Local wine boards dictate what kinds of grapes are used for the appellations. Italian Chianti's are made with sangiovese grapes, and French Chablis are made from chardonnay grapes. The only way to become familiar with which grapes make up which Appellations is to research the appellation you are interested in.
Where is the wine from? Varietals: What I'm about to say here will save your honey when picking out unfamiliar wines. Generally speaking: the more specific the wine label is in telling you where the grapes come from, the better chance you have of picking up a good wine.
For example, if one wine label says Washington Chardonnay, that could mean anything from a vineyard in the Columbia Valley or a winery right next to the Snohomish Slough. An entire state is a huge target to try to hit with a single dart. Who knows if you're going to get lucky in online casino. Besides, if a winery is only wants to be vague on where the grapes come from, do you really want to put your trust in them?
Granted, nowadays it is unlikely that you'll see wines with that large of an area to choose from. Most wineries know that it's profitable to put locations designated by an American Viticultural Areas. These areas are government defined locations that allow you to give a better estimation on where the grapes were grown. Often there'll be macro, and then micro AVA's within the Macro.
As an example, the Columbia Valley is an AVA that's pretty large - 185 miles wide and 200 miles long. But within that there are three micro: Walla Walla Valley, the Yakima Valley,and the Red Mountain AVA's. Reading Columbia Valley on a label would give you a general idea on where the wine has grown, but reading Yakima Valley on a label would give a more specific location. Some wineries may even tell you the specific vineyard that the grapes had been grown.