An ethnic group
peculiar to Pennsylvania
that is actually German
" is a corruption of the word deutsch
The Pennsylvania Dutch are today sometimes called Pennsylvania German (in the same spirit as the term "Native Americans"). The extent to which they have assimilated varies widely. Some Pennsylvania Dutch are Amish; these tend to be the most cloistered variety. Others are Mennonites, others are neither.
The Pennsylvania Dutch have their own dialect of the same name, but often called dutchie (thanks Qeyser) descended from High German but quite different. However, they traditionally still use Bibles written in Middle High German, which is a dead language just about everywhere else. Virtually all speak English, as a second or first language.
Pennsylvania Dutch (again, depending on how much they have assimilated) usually have very distinctive German features, dress, and accents, and often refer to non-Pennsylvania Dutch as "the English."