“Snifter” glasses are available in many sizes and variants, but they are often shaped like a Cognac glass. They are considered a glass for beer connoisseurs because the shape of the glass makes it easy to “sniff" the beer. To aid the “sniffing” the glass should not be filled to the brim. You want to be able to swing that beer around to release the wonderful aromas. When you swing a beer, you remove some of the carbon dioxide and that enables you to taste the beer even more. 

So, if you love to dwell on the taste of an IPA or a strong dark ale, this is the glass for you.