We went on a train trip recently and sat near a group of Amish. At first, I only met one man by himself, of about my age, standing by the window. In his vest, hat, pageboy haircut with beard, and John Lennon glasses, I at first took him for a hippie resident of Berkeley or Santa Cruz.
We have a couple of large-ish Mennonite communities here, and my husband’s co-worker friend, another software engineer, is Mennonite.
Nope.
Pennsylvania Dutch is a cultural designation (or perhaps linguistic, if you consider the PA dutch dialect to be a defining criteria), not a religous one. The term refers to the decendents of early settlers that William Penn recruited from the Rhine Valley and surrounding areas in what is now (mostly) Germany. Penn offered land, and a promise of religous freedom both of which were fairly attractive, as this area of europe was involved in some pretty hefty warfare at the time (much of it with a religous flavor, as it was wise to at least appear to practice the same religous beliefs as the area landholder).
Some of the original PA Dutch settlers practiced anabaptist religions, including the Amish, the Mennonites (and these are different (but similar) religions, not varying “degrees of isolation”), the Swenkfelders, and many many others (including several which refer to their members as “brethern”). But many other original PA Dutch settlers were Lutherens, or Catholics. It’s just that these religions had larger followings, and therefore never became linked with the PA Dutch in people’s minds. One of the oldest Catholic churches in PA is in a strong PA Dutch area, and was founded by some of those very settlers Penn rounded up in Germany.
While it is still correct to say that most modern day Amish ( and isn’t that an odd phrase 
) do come from PA Dutch cultural heritage, and many speak the PA Dutch dialect as their primary language at home, it is far from correct to imply that all PA Dutch are belivers in one of the anabaptist sects.
The PA Dutch are an extremely long surviving island of culture. Most PA dutch families are 200-250 years or more removed from Germany, and yet they remain identifable here in the US.
My family is PA Dutch, and have lived in Berks County PA or surrounding areas for the last 250 years. However, my Grandfather (born in 1915, less than 40 miles from Philadelphia) spoke PA Dutch as his primary language, and only learned English as a teenager. Historically speaking, my ancestors were mostly Lutheren (with a few Catholics), not anabaptists, and believe me, I’m far from Amish.
And for the OP. Amish communities separate themselves from the outside world by forgoing the use of technology and the trappings of the modern world. What this means specifically is defined by each individual community. There is no single rule book. 150 - 200 years ago, the Amish didn’t appear outwardly much different from their “English” neighbors, most of whom were also farmers [ Note: “english” is a term used by the Amish to refer to their non-amish neighbors, most of whom speak English as their primary language. It has nothing to do with actually being from England or of English decent] . Now, as the modern world evolves and changes faster and faster, and technology takes an ever increasing role in all of our lives, their lifestyle seems strikingly different.
Increasing land prices in many areas have made it difficult for some Amish communities to maintain the primarily agricultural lifestyle they held in the past. It has simply become cost prohibative for each family to support themselves on their own farm. These communities often sanction “trade” with the “english”, producing furniture, crafts or foods for sale to the general public (like those you encountered in the Reading Terminal Market), or becoming involved in the tourist trade. Other communities have made the decision to allow their members to work for the “english” (construction or housekeeping are popular). In the course of employment, some Amish are permitted to use some technology that they would not be allowed to own for their personal use, they can ride in cars (but usually not drive them), use power tools, or vaccum cleaners etc. but what they can and cannot do is still largely decided by the community
The money earned in any of these pursuits belongs to the person/family who earned it. However the Amish function as a comunity in the truest sense of the word, and will not hesitate to lend or give funds to community members in need. For example, they do not use the “english” system of insurance, but rather assist their own in times of need. They use the same hospitals and doctors as everyone else, but they by cash of medical services. They are not required to contribute to Social Security, nor are they eligable to collect it’s benefits.
Sorry for the enormous post
I often travel some of the secondary roads between Carlisle and Shippensburg, where I often encounter Amish riding buggies. The first time was quaint. The second time was mildly annoying, and now I just pass them.
Robin
Another aspect of involvement with us ‘English’ are the Amish and Mennonites who join local volunteer fire companies. A friend who is Fire Chief of a Lancaster county company was telling of how the main street in town looks like Tour de France when the whistle blows with all of the bicycle Mennonites tearing through town to the fire station. At another department I was initially puzzled by a structure behind the station: it looked like a typical open sided covered pavilion for picnics and such, but it was equipped with what looked like a long raised bathtub in the center. Those members who have horse and buggy can shelter the animals and give them access to water while the member attends meetings, training, or fire calls. Very cool!
An extremely interesting movie is ‘Devils Playground’ which offers an insiders view of Rumspringa-the Amish custom of teenagers dressing English, driving cars, partying, and sowing their wild oats before making a decision to join the order and be baptised.
I grew up in a Mennonite dominated small town in Central Ohio and for the past 30 years have lived in a small Iowa town smack dab in the middle of a fairly extensive Amish community in Northeast Iowa and another in Southeast Minnesota. I can only second much of what Pandora had to say.
Some communities are stricter in separating themselves from contemporary society than others. The local Amish were once of the “hook and eye” persuasion – the use of buttons on clothing was a worldly display of vanity. They now use and display buttons as a matter of routine. The Hook and Eye elders died out and the group of pro-button elders took over. Not too many years ago there was a huge fiasco about Amish education and compliance with state mandated school standards that was only resolved with a legislative exemption for religious communities. The local Amish trade with the local English community, both as buyers and as sellers. Some stores and restaurants and shops proudly display a black felt broad brimmed hat on a plac as a sign of good relations with the Amish community.
While the Amish are changing and accommodating those changes and accommodations are only what is absolutely necessary to keep the community going. The big things like no electricity, no self propelled farm machinery, the use of draft horses, the use of buggies and wagons, and the plain dress will continue. Contact with the outside world will continue to be minimized and permitted only to the extent it is necessary to the economic and social viability of the community.
Because each community runs it own affairs and makes it own rules, and because there is no Amish Pope, it is difficult to make broad sweeping generalizations about things that “all” Amish think, believe and do.
Northwest Montana has a small community of Amish who build furniture. There was another group north of Missoula but the recently moved.
whistlepig
I have also encountered Amish in Belize, Bolivia and Argentina. In Bolivia, they were mentioned as a ‘possible threat to national security.’ 
usually come up from the interior of Mexico to load up on dry goods - I’ve seen them walk out of fabric shops with hundreds of yards of material.
The Riddle of the Amish by Donald B. Kraybill is another good book.
And if you get the chance, see the documentary The Devil’s Playground. It’s about Amish teenagers celebrating “Rumspringa” or “the running around period” of their life. They are allowed to go into the English world for a time so that they can ultimately decide whether to stay in our world or go back to the Church.
I grew up in PA, and I’ve never heard all the names people are using for the different groups. Interesting!
The distinction I know of is “Old-order Mennonites”, who do the horse&buggy thing, vs. normal Mennonites, who are pretty much indistinguishable from the rest of us except for alot of names like Kroebel and Krauss.
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and it’s “Schwenkfelders”
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The best unexpected thing I saw on a road trip in Indiana was an Amish farmer plowing his field with a draft horse as his wife cut weeds in the yard with a gasoline weed whacker.
Thank you for all the fascinating replies to my initial inquiry about the Amish. I grew up as a Utah Mormon and some of my fascination circulates around the whole “in the world but not of the world” that fundamentalist Mormons and Amish/Mennonites might share 
Do most young Amish return to their communities after Rumpspringa? Can you ever go back after making a decision to leave when you’re a teenager?
Addendum: I’m a new member and am wondering after what time lapse does it become bad manners to respond to a dormant thread and bring it back to the top?