What is the difference between "European Butter" and American butter? I am in America, recently I noticed in my grocery store in the last year or two that there is a type of butter called "European Butter".

Is "European Butter" really different from regular butter, yes/no?

If yes, what is the difference between regular butter and "European" butter?

p.s. I thought there was only one way to make butter. So... is there such a thing as "European Butter" or is "European Butter" just made with different type of cow milk (i.e. a more organic... more grass fed.... less processed type of milk... maybe less homogenized)?
Most butter in the US is sweet cream butter, meaning that the cream is not cultured before it is churned. European style butter is cultured by adding bacteria to the cream and giving it time to thicken and acidify before churning. This results in subtle flavor changes. European style butter also has a slightly higher fat content. 

FWIW, imported and domestic cultured butter is becoming pretty common on US shelves. Expect to pay considerably more for it.