The term vintage has two meanings in the wine world - the year in which grapes making a particular wine come from; and the physical process of grape harvesting and winemaking. A vintage wine thus means the grapes used to make this wine come from a particular single year. As weather varies from one year to another and is never identical, the grapes grown and wines made each year are also unique. Therefore it is hardly surprising to find same wines from different vintage years taste totally different.
Of course, different winemaking techniques are also accounted for the change in wine characteristics, but the variation of grapes conditions from different growing seasons/years is the major determining factor for wine style and quality. After all, great wines must come from great grapes is an undeniable truth and what human intervention can do has its limitations. Basically, if in a particular year the grape growing season is perfect for making unique and stunning quality wines, then the wines coming from that vintage will taste much better than from other vintages. Bear in mind however, that vintage year alone is not a tag for quality indication; there are so many factors out there all contributing to the overall quality of finished wines.
The wines we enjoy nowadays generally have specified vintage years and you can easily identify them from the bottle labels. Some exceptions however, are Champagnes,Ports, Sherries and some sweet wines. Many cask wines are also without specific vintage years. In most circumstances, vintage wines are commonly regarded as superior to non-vintage wines. However, for top producers, vintage and non-vintages wines are basically different styles of wines. In the case of Champagnes, Ports and Sherries, non-vintage wines are made by blending older wines with newer wines for the purpose of quality and taste consistency. They are produced with maintaining certain styles in mind so consumers can enjoy their favourite brands every year without the risk of disappointment.
Vintage wines however, are a quite different story. In some great vintage years, the quality of grapes can be so outstanding that the winemakers think these fruits deserve to be made to express the perfection of these vintage years (eg. Fonseca Vintage Port 2011). Vintage wines can therefore be very different in flavour and style when tasted with its non-vintage siblings.
