Ever wonder why people swirl their glass of wine? Is this just something that wine snobs do? Or is it a kind of nervous habit? Are they doing it so they can examine the 'legs' of the wine? Or, are they doing it just to look cool? What's the point?
Well, there are two basic reasons to swirl a glass of wine; aeration and aromas.
First, aeration. This is simply adding air to the wine. This seem odd at first. Why does wine need air? After all, it's been intentionally stored in an air-tight bottle for some time. Well, with most red wines (typically the younger wines), adding air helps improve the flavor of the wine. Some of the improvement is due to the fact that evaporation occurs when you swirl which releases some of the stronger, less appealing compounds in the wine. But, overall, swirling allows the wine to get exposure to air which helps improve the flavor. The act of swirling the wine in the glass allows the wine to coat the inside of the glass, giving the wine more surface area and hence, more exposure to air.
Second, while you are swirling the wine and coating the inside of the glass, you are filling your glass with the wine's aromas - all those wonderful scents associated with the particular wine. This allows you to sniff the wine and to fully enjoy the wine experience on your tongue and in your nose. Both of which are very important to enjoying any flavorful food or drink.
But you don't want to swirl all wines. Sparkling wines (or 'Champagne') should not be swirled. This will quickly release all those wonderful bubbles and lead to a less-sparkling experience.
As to swirling a glass of wine to examine its legs (those tear drops that slide down the inside of a wine glass), it may be fun to watch, but it really doesn't tell you anything about the quality of the wine, just that it has alcohol in it.
So, go ahead and carefully swirl your wine. Yes, it may look cool, but it is actually helping the wine and improving your experience of the wine. Cheers!