It's eggnog season. But what's actually in this popular Christmas-time beverage?

Eggnog: the drink that indirectly led to grandma getting run over by a reindeer.

It's finally that time of year again, when grocery stores start stocking up on eggnog and polarize consumers, who usually fall into either the camp who loves the seasonal beverage and those who think it's super gross.

"I like eggnog, but it is super seasonal for me," Deke Dunne, beverage and creative director at the Eaton Hotel's Allegory and Wild Days bars in Washington, D.C., tells USA TODAY. "It is usually so thick and viscous, even though there are recipes that are more light-bodied, you don't want to drink a lot of it. I also associate the flavor profile with that late autumnal, early vernal time of year that it feels out of place if I drink it any other time of year."

As we've finally reached that point in the year where it's socially acceptable (at least, to some) to start pouring the eggnog, we're breaking down what exactly the beverage is — and how best to drink it, if you so choose.

What is eggnog? What is eggnog made of?

Eggnog consists of eggs beaten with sugar and milk or cream. Liquor is often added to that base, and it's usually consumed around the holidays, not as a year-round beverage. ("It is a lot of dairy," Dunne adds.)

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Is eggnog an alcoholic drink?

As it's sold, eggnog is usually not an alcoholic drink. But it's frequently used as the base of Christmas holiday cocktails. And the original eggnog recipes, which date back to the 1700s, included alcohol.

If you do opt to put the "spirit" in holiday spirit this season, Dunne recommends going with a dark liquor.

More: 60 fresh spins on eggnog across America

"I think that the best alcohol is a barrel-aged rum made from molasses or demerara sugar or a bourbon or scotch that has spent a decent amount of time in a barrel," he says. "Cognac can also be an amazing addition. Barrel-aged rums made from molasses or demerara take on such an amazing profile that perfectly fits eggnog. In a lot of those types of rums you get caramelized brown sugar, maple, cinnamon, nutmeg, molasses and vanilla. That is exactly what you want your eggnog to taste like."

This article originally appeared on USA TODAY: What is eggnog? What to know about the Christmas drink