There are billions of fonts out there, which makes it darned difficult to identify one by sight. That's doubly difficult if someone presents you with a graphic of a font. You can't exactly look that one up in the font drop-down menu in Word.
Instead, you plug it into What the Font?! In their words, "Upload a scanned image of the font and instantly find the closest matches in our database."
And it works amazingly well for identifying a mysterious typeface.