Let’s face it: Wine language is confusing.

Many of the world’s finest wines (and many more inferior ones) are aged in oak barrels, but if a wine tastes “oaky,” well, that means it tastes like a tree. And if there’s one thing we should all be able to agree on, repeat after me: Wine should not taste like a tree.

So why age wine in oak barrels? Is the barrel room merely a trophy case for millionaires looking to buy into the winery lifestyle? It is certainly effective bait for tourists. A stack of barrels holds the promise of wines to be enjoyed in the future. We smell the heady mix of wood and wine. If we’re lucky enough to be offered a barrel tasting, we salivate with expectation as the winemaker loosens the plastic bung and uses a glass “thief” to draw a sample and squirt the inky juice into our glasses. There’s a sense of adventure to a barrel tasting, as though we are stealing a bit of the future. Even when we are just visiting, we are witnessing the transition of last year’s vintage into next year’s new release — or so we think.

Something is happening, though. Those barrels are more than expensive decoration. They contribute structure, body and tannin to the wine, while helping to clarify and stabilize it. They also expose the wine to a measure of oxygen (through the wood, but also when the wine is “racked” from one barrel to another to remove the juice from the lees, or sediment), softening the wine and giving it a fleshier mouth feel.

As long as it doesn’t overwhelm the fruit, oak contributes many of the flavors we associate with fine wine. To taste oak’s influence, compare a barrel-fermented chardonnay with one labeled “unoaked.” The latter will taste fruity, while the barrel-fermented one will most likely taste spicy, with flavors of clove, nutmeg and vanilla. It may also have the drying sensation of tannins (though that typically is more noticeable in red wines). If you sense toast or smoke, that’s most likely barrel influence as well.

The oak flavor varies, depending on where the barrel is from and how it was made. French oak imparts flavors different from American oak, primarily because of the contrast in the grain of the wood. French barrels are considered the crème de la crème, but winemakers will buy barrels from several coopers, made of wood from different forests, to achieve variations in flavor for their wines.

The amount of toast, or charring when the staves are molded into shape, also affects flavor. If you detect coffee or smoke flavors in your reds, that’s probably from the oak. Wine critic Robert M. Parker Jr., of the Wine Advocate, uses “pain grillé,” or grilled bread, to describe that flavor — evoking something more complex than mere toast.

New barrels impart more assertive flavors than do older barrels that have been used in prior vintages. In recent years, winemakers have tended to use fewer new barrels in order to avoid overpowering the wines. That’s why so many wineries talk about how much new oak they use on their chardonnay or cabernet: They are giving us clues about how the wines were made and how they should taste.

Barrels are quite expensive and have risen dramatically in price over the past few years. That’s another reason winemakers are dialing back on their use of new ones. Boxwood Estate winery in Middleburg, Va., ages its red Bordeaux-style blends in barrels, about 30 percent of them new, according to Rachel Martin, the winery’s executive vice president. She pays $1,000 per barrel, including shipping from France.

“That means I pay $750 for the barrel and $250 for the air inside,” she quips. At about 28 cases of wine per barrel, that adds $3 per bottle to the winery’s cost. Magnify that over the wholesale and retail markups, and it’s easy to see how barrel aging adds to the cost of a wine.

So if you taste spicy, toasty flavors of oak in your inexpensive wine, they most likely don’t come from barrels. Winemakers soak oak chips in the wine or insert wood staves through stainless-steel tanks to impart those flavors on the cheap. Such oak treatment does not give the long-term structural benefits of barrel aging, but it can add complexity of flavor. Just so long as it doesn’t make the wine taste like a tree.

McIntyre blogs at dmwineline.com. On Twitter: @dmwine.

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